Display of generalized anaglyphs without retinal rivalry

ABSTRACT

General anaglyphs may be rendered using multiple primary colors to display the first and second images of stereoscopic images. De-saturated primary colors are advantageous for rendering anaglyphs in six, five, four, and three primary colors. A white primary color is advantageous for displaying a monochrome second image with a color first image. General anaglyphs may be dynamically created by a display apparatus using certain transformations and communication with external sources. Colored viewing filters with de-saturated transmission spectra provide better color when viewing anaglyph images.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. No. 8,194,119 B2. Thisapplication claims the benefit of U.S. patent application Ser. No.12/152,044 filed of date May 12, 2008, Provisional Application Ser. Nos.60/928,520 filed of date May 10, 2007, 60/932,354 filed of date May 31,2007, 60/994,001 filed of date Sep. 17, 2007, U.S. 60/997,931 filed ofdate Oct. 9, 2007, and 61/005,920 filed of date Dec. 10, 2007 all ofwhich are incorporated herein in its entirety by reference thereto.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

Not Applicable

BACKGROUND

Stereoscopic images generally consist of two images which are related bya small change in the lateral perspective. When viewed using an enablingapparatus, stereoscopic images may allow the perception of stereoscopicdepth. Anaglyphs are stereoscopic images wherein different primarycolors are used to render the first and second images of the stereopair. Usually the spectra of the first and second images do notsubstantially overlap each other. Then the first and second images maybe viewed selectively using two complementary color viewing filters. Thefirst viewing filter F₁ may be used to view the first image while thesecond viewing filter F₂ may be used to view the second image. The firstfilter substantially transmits the primary colors of the first image andblocks the primary colors of the second image. The second filtersubstantially transmits the primary colors of the second image andblocks the primary colors of the first image.

Anaglyphs are often rendered in three primary colors where the firstimage is rendered in two primary colors while the second image isrendered in one primary color. In red/cyan anaglyphs, the first image isrendered in green and blue primary colors while the second image isrendered in a red primary color. Other types of anaglyphs may includeblue/yellow and green/magenta anaglyphs. Herein these anaglyphs arecalled three-color anaglyphs.

Three-color anaglyphs are often used to display stereoscopic images dueto their relatively low cost and wide compatibility with conventionaldisplay apparatus. However, conventional three-color anaglyphs have somewell known disadvantages. Firstly, conventional three-color anaglyphsgenerally exhibit a reduced color gamut when viewed through the coloredviewing filters. Secondly, conventional anaglyphs generally exhibitretinal rivalry which may cause user discomfort. The prior art containsmany methods to improve the color gamut of anaglyphs. The prior art alsocontains many methods to reduce the retinal rivalry in anaglyphs.However, these anaglyphs still have reduced color gamuts or exhibitretinal rivalry.

It is well known that viewing a subject through colored filters mayreduce the observed color gamut of the subject. In general, a colorfilter which transmits only a single primary color may not allow anycolor hue to be fully perceived through the filter. For example, animage rendered in a pure red primary color may appear to be nearly agrayscale image when viewed through the red filter. On the other hand, afilter which transmits two primary colors may allow only the huesassociated with the two primary colors to be perceived through thefilter. The hue consisting of both primary colors may appear to benearly a gray color through the filter. For example, a cyan filter(which transmits green and blue light) may allow only blue and greenhues or blue and greenish-yellow hues to be perceived through the filterdepending on how close the green primary color is to yellow. An imagerendered in pure cyan hues may appear to be nearly a grayscale imagewhen viewed through a cyan filter. These phenomena may be confirmed byviewing a digital color spectrum through pure cyan and pure red filters.Software programs for editing digital images often provide a suitabledigital color spectrum in their color selection tools.

Since the second image in an anaglyph, may be generally perceived as agrayscale image, the color gamut observed in a stereo view of aconventional anaglyph may be generally similar to the color gamut of thefirst image rendered in two primary colors. In other words, the firstimage in an anaglyph generally contributes more to color perception thanthe second image. From these observations, one might expect that onlyblue and yellowish-green hues may be perceived in red/cyan anaglyphs.However, additional color hues are often visible in conventionalred/cyan anaglyphs due to the effects of retinal rivalry.

One common method of creating red/cyan anaglyphs combines the green andblue primary channels of the first image with the red primary channel ofthe second image. This type of anaglyph is often called a “true-color”anaglyph. Surprisingly, red and cyan hues may be perceived in sometrue-color anaglyphs when viewed through red and cyan viewing filters.In other words, while the single filters do not allow red or cyan huesto be perceived, the stereo view through the two filters may allow redand cyan hues to be perceived. However, the red and cyan hues aregenerally accompanied by large amounts of retinal rivalry. Similarphenomena occur in analogous blue/yellow and green/magenta true-coloranaglyphs.

True-color anaglyphs generally contain too much retinal rivalry forcomfortable viewing. Therefore many methods have been developed in theprior art to produce anaglyphs with less retinal rivalry than observedin true-color anaglyphs. In order to observe less retinal rivalry,anaglyphs are often constructed from images with modified colors. Thesecolor modifications may reduce the retinal rivalry observed in theanaglyph, but may also reduce the spectrum or saturation of huesperceived in the anaglyph. Herein these anaglyphs with modified colorsand rendered in three primary colors are called partial-color anaglyphs.

There are various editing operations which may be applied tostereoscopic images prior to constructing an anaglyph which are known toreduce retinal rivalry. These may include de-saturation of hues and huesubstitution. Many methods involve local editing of an image so that theediting functions vary throughout an image. These are relatively laborintensive and expensive methods to prepare anaglyphs. A particularmethod of the prior art may cause an average reduction of retinalrivalry in a stereo view while patches of high retinal rivalry remainscattered throughout the stereo view. However, the prior art does notprovide a method to reduce the retinal rivalry to arbitrarily low levelsfor any distribution of initial color content in a stereoscopic image.The prior art lacks a working theory of how to avoid retinal rivalrywhen producing partial-color anaglyphs.

The conditions which are required to avoid retinal rivalry in coloranaglyphs are not described in the prior art. Generally, the prior artcontemplates a compromise between the color gamut and the level ofretinal rivalry observed in an anaglyph. It is widely believed thatretinal rivalry is necessarily present to some degree in coloranaglyphs. In order words, it is widely believed that all coloranaglyphs contain more retinal rivalry than grayscale anaglyphs. Mostefforts of the prior art have been directed toward improving the colorgamut of partial-color anaglyphs while accepting a reduced butsubstantial amount of retinal rivalry.

Methods exist in the prior art to increase the color gamut of anaglyphsby using leaky viewing filters. It is well known that the range ofperceived hues in partial-color anaglyphs may be expanded to some degreeby allowing one or both of the viewing filters to partially transmit orleak a small amount of additional primary colors through the filters.For example, a red filter which also transmits a small amount of greenlight may allow an unsaturated green hue and an unsaturated red hue tobe perceived through the red filter. Or a cyan filter which alsotransmits a small amount of red light may allow an unsaturated red hueand an unsaturated cyan hue to be perceived through the filter. However,transmitting part of the primary colors of the opposite image throughthe viewing filters may cause the user to see ghost images or doubleimages in the stereo view. The double images may reduce the ability ofthe user to fuse the stereo pair and may reduce the perceivedstereoscopic depth in the stereo view. Therefore, when using leakyfilters, the benefit of the extra hues created by the leak must bebalanced against the disadvantage of perceiving less stereoscopic depth.

Conventional cyan filters for viewing red/cyan anaglyphs are oftendesigned to leak a small amount of a red primary color through thefilter. This allows a weak reddish hue to be perceived through the cyanfilter. However the leaked red primary color creates a ghost of thesecond image in the view of the first image. Furthermore since thesecond image may be offset from the first image due to stereoscopicparallax, the red light from the second image may not always be at theproper location to contribute correctly to the color of the first image.Similar disadvantages occur when using leaky filters with blue/yellowand green/magenta anaglyphs.

The prior art contains methods to predict the color gamut observed inanaglyphs viewed through leaky filters using conventional color modelssuch as the CIE (International Commission on Illumination) RGB colormodels. The CIE color models were developed for red, green and blueprimary colors. However, it is clear that color perception may bedrastically changed by color viewing filters. For example, a red viewingfilter may change a red color, which is considered a dark color inconventional color models, into a white color which is a bright,unsaturated color. Therefore, applying conventional color modelcalculations to predict the color gamut perceivable through colorfilters has questionable meaning. Furthermore, the color gamutperceivable in an anaglyph depends on the amount and distribution ofretinal rivalry. In fact, the effects of retinal rivalry on theperceived color gamut is often greater than the effect of leakingcomplementary colors through the filters. This is a further reason thatcolor gamut calculations based on conventional color models have limitedmeaning when applied to conventional anaglyphs.

Grayscale anaglyphs are anaglyphs which are constructed from grayscaleversions of stereoscopic images. The grayscale values of the first imageare displayed in two primary colors while the grayscale values of thesecond image are displayed in the remaining primary colors. A grayscaleanaglyph may appear grayscale when viewed through the anaglyph viewingfilters. Grayscale anaglyphs have the advantage of having nearly noperceivable retinal rivalry, but have the disadvantage of not providingcolored stereo views. Herein, an anaglyph may be considered to be acolor anaglyph unless otherwise stated.

The prior art contains a method to display stereoscopic image using sixprimary colors with non-overlapping spectra. The first image may bedisplayed in red R₁, green G₁ and blue B₁ primary colors. The secondimage may be displayed in red R₂, green G₂ and blue B₂ primary colors.The spectra of the primary colors do not substantially overlap. A firstviewing filter F₁ substantially transmits the red R₁, green G₁ and blueB₁ primary colors and blocks the red R₂, green G₂ and blue B₂ primarycolors. A second viewing filter F₂ substantially transmits the red R₂,green G₂ and blue B₂ primary colors and blocks the red R₁, green G₁ andblue B₁ primary colors. The first viewing filter F₁ may be used toselectively view the first image while the second viewing filter F₂ maybe used to selectively view the second image. The primary color spectraare such that the spectra of the primary color R₁ is positioned atshorter wavelengths than the spectra of primary color R₂, the spectra ofthe primary color G₁ is positioned at shorter wavelengths than thespectra of primary color G₂, and the spectra of the primary color B₁ ispositioned at shorter wavelengths than the spectra of primary color B₂.This method of displaying stereoscopic images has the disadvantage ofthe viewing filters being relatively expensive to manufacture. Also themethods of displaying stereoscopic image with the six primary colors{R₁, R₂, G₁, G₂, B₁, B₂} described in the prior art produces retinalrivalry for some distribution of hues in the stereoscopic image.

A white primary color is often used in digital display apparatus inorder to increase the brightness of the display apparatus. The whiteprimary color is often beneficial for displaying white backgrounds suchas a white background against black text. The white primary color mayalso be used to increase the brightness of images. In this case, someloss of saturation of the images usually occurs. A display with a whiteprimary color W usually also has red R, green G and blue B primarycolors. Therefore displays with a white primary color often provide atotal of four (or more) primary colors {R, G, B, W}. In the prior art,the spectra of the primary color W overlaps the spectra of the primarycolors {R, G, B} and their polarization states are usually identical.

Four (or more) primary colors may be provided in a projector by (1)using four (or more) segments in a color filter wheel, or (2)time-multiplexing the light source where the light source may be LED'sor laser diodes, or (3) using four micro display devices, or (4) using afour-color pixel format in a micro display device or (5) some othermethod. Hybrids of these methods can also be used. Four primary colorscan be provided in a flat panel display by using a four-color pixelpattern. Flat panel displays may include LCD displays and plasmadisplays.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to the use of primary colors, colortransformations, and special filters to display and view digitalanaglyphs with wide color gamuts without retinal rivalry.

The present invention involves the concept of brightness contrast in thefirst and second images of a stereoscopic image. If the brightnesscontrast is balanced in the first and second images, the stereo view ofthe stereoscopic image may be free of retinal rivalry andfull-stereoscopic depth may be perceived. Anaglyph stereoscopic imagestypically do not provide balanced brightness contrast due to thedifferent primary colors used in the first and second images. Thepresent invention provides methods of display anaglyph images withbalanced brightness contrast for any set of primary colors used for thefirst and second images.

A general class of anaglyphs is defined in which the spectra of theprimary colors of the first and second images are not identical.Anaglyphs have the property that the color transformations of thepresent invention are generally required in order to balance thebrightness contrast in the anaglyph. If the brightness contrast isbalanced, the color gamut of anaglyphs is often dominated by a firstimage of the anaglyph having a greater number of primary colors.Anaglyphs displayed with three primary colors of the present inventiongenerally have incomplete color gamuts where about half the hues of acolor wheel may be observed. Anaglyphs displayed with four primarycolors of the present invention may be full color gamuts. Anaglyphsdisplayed in five and six primary colors may have full color gamuts.

Since increasing the number of primary colors of an anaglyph mayincrease the cost of complexity or reduce the performance of a displayapparatus, it may be advantageous to use as few primary colors aspossible that provide a full color gamut. Furthermore the cost ofviewing filters may increase substantially for each additional primarycolor. The present invention provides special sets of primary colorswhich allow relatively inexpensive viewing filter for four, five, andsix-primary-color anaglyphs. The present invention provides methods ofusing a white primary color to display the second image of an anaglyphdisplayed in four primary colors. The white primary color improves thewhite colors observed in the stereo view of the anaglyphs. A specialthree-primary-color anaglyph of the present invention uses a cyanprimary color for the second image and red and green primary colors forthe first image. The cyan primary color provides adequate brightnessrange to balance the brightness contrast of the first image.

The present invention provides methods to create and display anaglyphimages by a display apparatus. This allows stereoscopic images to bedistributed and stored in a standard full-color stereoscopic format anddisplayed in high quality anaglyphs. The present invention providesmethods to process full-color stereoscopic images and display then ashigh quality anaglyph images. The present provides methods to receivestereoscopic images, transform them into anaglyphs and display theanaglyphs at the rate of a non-stereoscopic images. The prior artgenerally creates anaglyphs before transferring them to a displayapparatus. Whereas the anaglyph of the prior art generally createretinal rivalry, the methods of the present invention may be used toavoid creating retinal rivalry. The present invention provides methodsto compress a four-color primary anaglyph into three channels. The threechannel format may be beneficial for cases when a communication port islimited to three channels.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 a depicts the spectra of conventional red Q₁, green P₂, and blueP₃ primary colors and the spectra of conventional red and cyan viewingfilters.

FIG. 1 b depicts red Q₁, green P₁, and blue P₂ primary colors on a CIEchromaticity diagram; and the one-dimensional color gamut of the primarycolors {P₁, P₂}.

FIG. 2 a depicts the spectra of yellow Q₁, red P₁, green P₂, and blue P₃primary colors; and the spectra of viewing filters F₁ and F₂ which maybe used to view anaglyphs displayed in the primary colors {P₁, P₂, P₃}and {Q₁}.

FIG. 2 b depicts yellow Q₁, red P₁, green P₂, and blue P₃ primary colorson a CIE chromaticity diagram; and the two-dimensional color gamut ofthe primary colors {P₁, P₂, P₃}.

FIG. 3 a depicts the spectra of red P₁, green P₂, and blue P₃ primarycolors; the spectra of red Q₁, green Q₂, and blue Q₃ primary colors; andthe spectra of viewing filters F₁ and F₂ which may be used to viewanaglyphs displayed in the primary colors {P₁, P₂, P₃} and {Q₁, Q₂, Q₃}.

FIG. 3 b depicts red P₁, green P₂, and blue P₃ primary colors and redQ₁, green Q₂, and blue Q₃ primary colors on a CIE chromaticity diagram;and the two-dimensional color gamut of the primary colors {P₁, P₂, P₃};and the two-dimensional color gamut of the primary colors {Q₁, Q₂, Q₃}.

FIG. 4 a depicts the spectra of red P₁, green P₂, and blue P₃ primarycolors; the spectra of red Q₁, green Q₂, and blue Q₃ primary colors; andthe spectra of viewing filters F₁ and F₂ which may be used to viewanaglyphs displayed in the primary colors {P₁, P₂, P₃} and {Q₁, Q₂, Q₃}.

FIG. 4 b depicts red P₁, green P₂, and blue P₃ primary colors and redQ₁, green Q₂, and blue Q₃ primary colors on a CIE chromaticity diagram;and the two-dimensional color gamut of the primary colors {P₁, P₂, P₃};and the two-dimensional color gamut of the primary colors {Q₁, Q₂, Q₃}.

FIG. 5 a depicts the spectra of red P₁, green P₂, and blue P₃ primarycolors; the spectra of yellow Q₁, and blue Q₂ primary colors; and thespectra of viewing filters F₁ and F₂ which may be used to view anaglyphsdisplayed in the primary colors {P₁, P₂, P₃} and {Q₁, Q₂}.

FIG. 5 b depicts red P₁, green P₂, and blue P₃ primary colors and yellowQ₁, and blue Q₂ primary colors on a CIE chromaticity diagram; and thetwo-dimensional color gamut of the primary colors {P₁, P₂, P₃}; and theone-dimensional color gamut of the primary colors {Q₁, Q₂}.

FIG. 6 a depicts the spectra of red P₁, green P₂, and blue P₃ primarycolors; the spectra of red Q₁, and cyan Q₂ primary colors; and thespectra of viewing filters F₁ and F₂ which may be used to view anaglyphsdisplayed in the primary colors {P₁, P₂, P₃} and {Q₁, Q₂}.

FIG. 6 b depicts red P₁, green P₂, and blue P₃ primary colors and redQ₁, and cyan Q₂ primary colors on a CIE chromaticity diagram; and thetwo-dimensional color gamut of the primary colors {P₁, P₂, P₃}; and theone-dimensional color gamut of the primary colors {Q₁, Q₂}.

FIG. 7 a depicts the spectra of red P₁, green P₂, and blue P₃ primarycolors; the spectra of red Q₁, and green Q₂ primary colors; and thespectra of viewing filters F₁ and F₂ which may be used to view anaglyphsdisplayed in the primary colors {P₁, P₂, P₃} and {Q₁, Q₂}.

FIG. 7 b depicts red P₁, green P₂, and blue P₃ primary colors and redQ₁, and green Q₂ primary colors on a CIE chromaticity diagram; and thetwo-dimensional color gamut of the primary colors {P₁, P₂, P₃}; and theone-dimensional color gamut of the primary colors {Q₁, Q₂}.

FIG. 8 a depicts the spectra of red P₁, and green P₂ primary colors; thespectra of yellow Q₁, and blue Q₂ primary colors; and the spectra ofviewing filters F₁ and F₂ which may be used to view anaglyphs displayedin the primary colors {P₁, P₂} and {Q₁, Q₂}.

FIG. 8 b depicts red P₁, and green P₂ primary colors and yellow Q₁, andblue Q₂ primary colors on a CIE chromaticity diagram; and theone-dimensional color gamut of the primary colors {P₁, P₂}; and theone-dimensional color gamut of the primary colors {Q₁, Q₂}.

FIG. 9 a depicts the spectra of red P₁, and green P₂ primary colors; thespectra of green Q₁, and blue Q₂ primary colors; and the spectra ofviewing filters F₁ and F₂ which may be used to view anaglyphs displayedin the primary colors {P₁, P₂} and {Q₁, Q₂}.

FIG. 9 b depicts red P₁, and green P₂ primary colors and green Q₁, andblue Q₂ primary colors on a CIE chromaticity diagram; and theone-dimensional color gamut of the primary colors {P₁, P₂}; and theone-dimensional color gamut of the primary colors {Q₁, Q₂}.

FIG. 10 a depicts the spectra of red P₁, and green P₂ primary colors;the spectra of a cyan Q₁ primary color; and the spectra of viewingfilters F₁ and F₂ which may be used to view anaglyphs displayed in theprimary colors {P₁, P₂} and {Q₁}.

FIG. 10 b depicts red P₁, and green P₂ primary colors and cyan Q₁primary color on a CIE chromaticity diagram; and the one-dimensionalcolor gamut of the primary colors {P₁, P₂}.

FIG. 11 a depicts a display apparatus receiving stereoscopic images indisplay coordinates {P}, and {Q} into first and second buffers {U} and{V} from an external source through two communication ports {C} and {D}.

FIG. 11 b depicts a display apparatus receiving stereoscopic images incoordinates {A}, and {B} into first and second buffers {U} and {V} froman external source through two communication ports.

FIG. 12 a depicts a display apparatus receiving a first image incoordinates {A} into a first buffer {U} from an external source throughone communication port {C}.

FIG. 12 b depicts a display apparatus receiving a second image incoordinates {B} into a second buffer {V} from an external source throughone communication port {C}.

FIG. 12 c depicts a display apparatus loading the coordinates {P} and{Q} of an anaglyph into the primary colors {T} of the display apparatus.

FIG. 13 a depicts a display apparatus receiving a first image incoordinates {A} into a buffer {U} from an external source through onecommunication port {C} and transforming the coordinates {A} into displaycoordinates {P}.

FIG. 13 b depicts a display apparatus receiving a second image incoordinates {B} into a buffer {U} from an external source through onecommunication port {C} and transforming the coordinates {B} into displaycoordinates {Q}.

FIG. 13 c depicts a display apparatus loading the coordinates {P} and{Q} of an anaglyph into the primary colors {T} of the display apparatus.

FIG. 14 a depicts a display apparatus receiving a stereoscopic image incoordinates {E} into a buffer {U} from an external source through onecommunication port {C} and transforming the coordinates {E} intoanaglyph coordinates {P} and {Q}; and loading coordinates {P} and {Q} inthe primary colors {T}.

FIG. 14 b depicts a method of compressing coordinates {P₁, P₂, P₃} and{Q₁} into three channel coordinates {E₁, E₂, E₃}.

FIG. 15 a depicts a method of compressing coordinates {P₁, P₂, P₃} intotwo channel coordinates {E₁, E₂} using chromaticity coordinates.

FIG. 15 b depicts a method of compressing coordinates {P₁, P₂, P₃} intotwo channel coordinates {E₁, E₂} using reduced resolution red, green,and blue coordinates.

FIG. 16 depicts a four LCOS display panel assembly for projecting fourprimary color {P₁, P₂, P₃, Q} images.

FIG. 17 depicts three LCOS display panel assembly for projecting fourprimary color {P₁, P₂, P₃, Q} images.

FIG. 18 a depicts a LCD display panel assembly for projecting fourprimary color {P₁, P₂, P₃, Q} images.

FIG. 18 b depicts a color wheel with a pattern of color filters.

FIG. 19 depicts a DMD display panel assembly for projecting four primarycolor {P₁, P₂, P₃, Q} images.

FIG. 20 depicts a LCD display panel assembly for projecting four primarycolor {P₁, P₂, P₃, Q} images.

FIG. 21 depicts a pixel pattern providing four primary colors {P₁, P₂,P₃, Q}.

FIG. 22 depicts a pixel pattern providing four primary colors {P₁, P₂,P₃, Q}.

FIG. 23 depicts a LCD display panel with a time sequential backlight.

FIG. 24 depicts a LCD display panel with a patterned polarizationrotator layer.

FIG. 25 depicts a LCD display panel with a CSPF polarization rotatorlayer.

FIG. 26 depicts two projectors with two external filters.

FIG. 27 depicts a projector with a movable internal filter.

FIG. 28 a depicts a projector projecting a stereoscopic image through anoptical device.

FIG. 28 b depicts a stereoscopic image from a projector and on a screen.

FIG. 29 a depicts a projector projecting a stereoscopic image through anoptical device.

FIG. 29 b depicts a stereoscopic image from a projector and on a screen.

FIG. 30 depicts a projector apparatus with one objective lens.

FIG. 31 depicts a projector apparatus with two objective lenses.

DETAILED DESCRIPTION OF THE INVENTION

Additional information can be found in United States patent applicationserial number 2008/000835 by inventor Monte J. Ramstad which isincorporated in its entirety by reference hereto.

Additional information can be found in United States patent applicationserial number 2008/000841 by inventor Monte J. Ramstad which isincorporated in its entirety by reference hereto.

Additional information can be found in United States patent applicationserial number 2008/000855 by inventor Monte J. Ramstad which isincorporated in its entirety by reference hereto.

Additional information can be found in a co-pending United States patentapplication titled Universal Stereoscopic File Format by inventor MonteJ. Ramstad which is incorporated in its entirety by reference hereto.

Generalized Anaglyphs

In general, a display apparatus may display stereoscopic images using aset of primary colors S₁={P₁, . . . , P_(m)} to display the first imageand a set of primary colors S₂={Q₁, . . . , Q_(n)} to display the secondimage. Herein a primary color is light in a distribution of wavelengthswhere the intensity of the light may be varied independently. Theintensity of each primary color may be varied independently from theintensity of other primary colors. Herein anaglyphs are defined to bestereoscopic images displayed in primary colors {P₁, . . . , P_(m)} and{Q₁, . . . , Q_(n)} where at least one primary color (spectra) P_(i) inthe set of primary colors S₁={P₁, . . . , P_(m)} of the first image isnot present in the set of primary colors S₂={Q₁, . . . , Q_(n)} of thesecond image. Herein, the number of primary colors provided by a displayapparatus is assumed to be three or more. Therefore, it is assumed thatm+n>2. Anaglyphs of the present invention may have either polarized ornon-polarized primary colors. Anaglyphs of the present invention may beviewed with any stereoscopic viewing technology such as colored filterglasses, polarized filter glasses, side-by-side viewers, head mounteddisplays, or autostereoscopic screens. Stereoscopic images which aredisplayed using primary colors having identical spectra for the firstand second images are not considered to be anaglyphs herein.

Since the primary colors in the first and second images of an anaglyphare not identical, the brightness contrast of like subject matter in thefirst and second images may be unbalanced. Unbalanced brightnesscontrast is often associated with retinal rivalry in the stereo view ofa stereoscopic image. Therefore retinal rivalry may be observed inanaglyphs unless the methods of the present invention are applied inorder to balance the brightness contrast in the first and second images.

Herein the term anaglyph refers to color anaglyphs when the contextimplies a color anaglyph.

The Stereoscopic Brightness Coordinate

The present invention identifies the color property which may besubstantially used by the visual system to process stereoscopicinformation. Herein this stereoscopic color property is calledbrightness contrast or brightness. The brightness may be considered acarrier of the brightness contrast in the image. When the brightnesscontrast is balanced in the first and second images for like subjectmatter, retinal rivalry may be essentially absent from the stereo viewand full stereoscopic depth (true-depth) may be perceived in a stereoview.

In stereoscopic images, retinal rivalry may be associated withunbalanced brightness contrast in the first and second images of thestereo view. For example in red/cyan anaglyphs, a red object, which mayappear relatively bright through a red filter and may appear relativelydark through a cyan filter, may cause retinal rivalry in a stereo view.Usually the human visual system does not stereoscopically fuse a darkobject observed by one eye with a bright object observed by the othereye. Instead, the user essentially experiences double vision where theleft and right eyes “see” independently. Then stereoscopic perceptionmay be much reduced or absent. (Stereoscopic perception requires thecooperation of both eyes.) In this way, the presence of retinal rivalryor unbalanced brightness contrast may be associated with less than fullstereoscopic depth perception in a stereoscopic image.

In general, retinal rivalry may be observed in stereoscopic images wherean edge in the subject matter may be observed with more brightnesscontrast in one eye than in the other eye. This suggests that balancingthe brightness contrast in all subject matter may eliminate retinalrivalry. Furthermore, stereoscopic fusion depends largely on the edgesof objects being observed by both eyes. Herein an edge may begeneralized to any type of brightness contrast in an image. In order forall edges to be equally detected by both eyes for all subject matter, itis apparently sufficient to observe balanced brightness contrast at allbrightness levels in the image. Herein the definition of balancedbrightness contrast in the first and second views is: the relativebrightness contrast in the two views which eliminates retinal rivalry inthe stereo view at substantially all brightness levels. By balancing thebrightness contrast in all subject matter observed by the left and righteyes in a stereo view, full-depth perception may be perceived in thestereo view.

The brightness of a color is generally an integral of the brightnesscontrast. Therefore, the present invention provides a definition ofbrightness. Determining a condition of balanced brightness may requirecomparing the brightness of various colors. The relative brightness ofdifferent colors may depend on subjective evaluation by users. Theapparent relative brightness of different colors may vary from user touser and may vary over time for the same user. The relative brightnessof different color hues may also depend on the size of a patch of acolor hue, the surrounding color hues, and on the vision adaptation ofthe user.

In the prior art, the term brightness is generally used to describe anobserved property of light rather than a physical property of light. Inthe present invention, brightness also describes an observed property oflight. However, in the present invention, brightness is defined by theabsence of retinal rivalry in a stereo view rather than the property ofa single image.

The brightness color property Y_(B) of the present invention may besimilar to the luminance coordinate Y in the CIE xyY color spaceshowever, the defining measurements are different. Some of thedifferences in the measurements of the brightness Y_(B) of the presentinvention and luminance Y of the CIE color models may include: (1) thebrightness Y_(B) may be determined while viewing through colored filterglasses whereas the luminance Y is determined using unfiltered vision;(2) the number of primary colors contributing to the brightness Y_(B)and the luminance Y may be different; (3) the color patch size may notnecessarily be fixed when determining Y_(B) whereas a standard patchsize is usually used to determine the luminance Y; (4) the brightnessY_(B) is defined by the observed retinal rivalry being minimized for alledges (or levels of contrast) whereas the luminance Y is defined byjudging the “brightness” of a single image; (5) the spectra of primarycolors contributing to the brightness Y_(B) and the luminance Y may bedifferent especially when brightness Y_(B) takes into account theeffects of the viewing filters on the primary colors; (6) the whitepoint of the color space may be shifted in the measurement of thebrightness Y_(B) due to the limited spectra of the viewing filters, (7)the brightness Y_(B) may include factors such as chromatic brightnessand vision adaptation. Herein, chromatic brightness may include theenhanced brightness observed in highly saturated colors, in colors thatinclude a narrow range of wavelengths of light, and in colors of variouspatch size.

Although the brightness Y_(B) and luminance Y properties are defineddifferently, in practice they may describe similar properties of light.Therefore in some embodiments of the present invention, the brightnessY_(B) and the luminance Y may be used interchangeably. The presentinvention may utilize any method of calculating the brightness Y_(B)which may include methods which follow by analogy from methods ofcalculating the luminance Y which may be described in the prior art ordeveloped in the future. Herein the brightness Y_(B) coordinate may alsobe called the luminance coordinate without loss of generality.

Displaying Anaglyphs with Balanced Brightness

One embodiment of the present invention provides a method of displayingstereoscopic images comprising a display apparatus providing primarycolors {P₁, . . . , P_(m)} for displaying a first image and providingprimary colors {Q₁, . . . , Q_(n)} for displaying a second image. Thefirst image may be representable in color coordinates {A₁, . . . ,A_(r)}. The second image may be representable in color coordinates {B₁,. . . , B_(s)}. The display apparatus may include a transformation G₁which transforms the coordinates {A₁, . . . , A_(r)} into the primarycolors {P₁, . . . , P_(m)} and a transformation G₂ which transforms thecoordinates {B₁, . . . , B_(s)} into the primary colors {Q₁, . . . ,Q_(n)} whereby the brightness displayed in the first and second imagesmay be balanced for like subject matter in the first and second images.The coordinates {A₁, . . . , A_(r)} and {B₁, . . . , B_(s)} may becoordinates of any color space from which the brightness of the firstand second images may be obtained.

The transformations G₁ and G₂ may be summarized as follows:

Typically stereoscopic images may be captured or created with balancedbrightness for like subject matter. Herein, the first and second imagesrepresented in coordinates {A₁, . . . , A_(r)} and coordinates {B₁, . .. , B_(s)} respectively have balanced brightness for like subjectmatter. The transformation G₁ may conserve the brightness contrast ofthe first image in the primary colors {P₁, . . . , P_(m)}. Thetransformation G₂ may conserve the brightness contrast of the secondimage in the primary colors {Q₁, . . . , Q_(n)}. Then the primary colors{P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} may display balancedbrightness contrast for like subject matter in the first and secondimages.

The transformation G₁ may be selected so that the brightness Y_(P)observed in the primary colors {P₁, . . . , P_(m)} may be balanced withthe brightness Y_(A) represented in the coordinates {A₁, . . . , A_(r)}.For example, if the brightness Y_(P) may be approximated byY _(P)=(β₁ P ₁ ^(γ′)+β₂ P ₂ ^(γ′)+β₃ P ₃ ^(γ′))^(1/γ′),and the brightness Y _(A) may be approximated byY _(A)=(α₁ A ₁ ^(γ)+α₂ A ₂ ^(γ)+α₃ A ₃ ^(γ))^(1/γ),the transformation G₁ may be selected so that brightness contrast ofY_(P) may be balanced with the brightness contrast of Y_(A),Y_(P)˜Y_(A).

Similarly, the transformation G₂ may be selected so that the brightnessY_(Q) observed in the primary colors {Q₁, . . . , Q_(n)} may be balancedwith the brightness Y_(B) represented in the coordinates {B₁, . . . ,B_(s)}. For example, if Y_(Q) may be approximated byY _(Q)=(δ₁ Q ₁ ^(γ′)+δ₂ Q ₂ ^(γ′)+δ₃ ^(γ′))^(1/γ′),and Y _(B) may be approximated byY _(B)=(ε₁ B ₁ ^(γ)+ε₂ B ₂ ^(γ)+ε₃ B ₃ ^(γ))^(1/γ),the transformation G₂ may be selected so that brightness contrast ofY_(P) may be balanced with the brightness contrast of Y_(A),Y_(Q)˜Y_(B).

Alternatively, the G₁ and G₂ transformations may be selected so that thedisplayed stereoscopic image has balanced brightness in the primarycolors {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)}, which may be a lessrestrictive condition on the transformations G₁ and G₂ than transformingthe brightness represented in the coordinates {A₁, . . . , A_(r)} and{B₁, . . . , B_(s)} into the primary colors {P₁, . . . , P_(m)} and {Q₁,. . . , Q_(n)} respectively.

Herein the values of the primary colors {P₁, . . . , P_(m)} and {Q₁, . .. , Q_(n)} may be considered the color coordinate values of a displayapparatus. The display apparatus may transform the coordinate valuesinto the physical primary colors {P₁, . . . , P_(m)} and {Q₁, . . . ,Q_(n)}. Herein the notation does not always distinguish between thecolor coordinates of the display apparatus and the physical primarycolors of a display apparatus although the distinction will be clearfrom the context to one skilled in the art.

In U.S. patent application serial number 2008/000835 of the presentinventor, methods to balance the brightness contrast of the primarycolors {P₁, . . . , P_(m)} and {Q₁} are described, and a calibrationbased on observation is described. In the present invention, thetransformations G₁ and G₂ may be selected to conserve the brightnesscontrast represented in the coordinates {A₁, . . . , A_(r)} and {B₁, . .. , B_(s)}, therefore, brightness calibrations based on observations maynot be required for the methods described herein. However observationsremain the foundation of the balanced brightness condition. The methodsof testing for balanced brightness contrast of the displayed imagesdescribed in U.S. patent application serial number 2008/000835 may beadapted to the present case of multiple primary colors {Q₁, . . . ,Q_(n)} used to display the second image. Therefore, the weaker conditionon transformations G₁ and G₂ which balances the brightness contrast ofthe displayed images rather than conserving the brightness contrast inthe coordinates {A₁, . . . , A_(r)} and {B₁, . . . , B_(s)} is withinthe scope of the present invention.

The transformation G₁ of the first image into the primary colors {P₁, .. . , P_(m)} which conserves the brightness contrast represented in thecoordinates {A₁, . . . , A_(r)} may be obtained as follows:

First, the coordinates {A₁, . . . , A_(r)} may be transformed intolinear brightness coordinates {A^(L) ₁, . . . , A^(L) _(r)}:A ^(L) _(j) =H _(Aj)(A _(j))using functions H_(Aj). The functions are the non-linearity functionsencoded into the coordinates of the first image. Linear brightnesscoordinates may be defined as color coordinates whose contribution tothe brightness of a color may be added together to obtain the totalbrightness of a color.

In some reference color spaces, the form of the H_(Aj) functions may beapproximated by gamma functions. For example in the sRGB color space,the functions H_(Aj) may be approximated by:H _(Aj)(A _(j))=A _(j) ^(γ)where γ may be about 2.2. Then the linear brightness Y^(L) _(A) of thefirst image may be obtained by adding the contribution of eachcoordinate to the brightness:Y ^(L) _(A)=Σ_(j)α_(j) A ^(L) _(j)=Σ_(j)α_(j) H _(Aj)(A _(j))where1=Σ_(j)α_(j).

The parameters α_(j) may be determined from observations. In a referencecolor space, the values of α_(j) may be known. For example in the sRGBcolor space, α₁ may be about 0.2126, α₂ may be about 0.7152, and α₃ maybe about 0.0722.

Second, a transformation M may be selected to transform the coordinatesA^(L) _(j) into the linear primary color values P^(L) _(k)=H_(P)(P_(k))of the display apparatus as followsP ^(L) _(k)=Σ_(j) M _(kj) A ^(L) _(j)=Σ_(j) M _(kj) H _(Aj)(A _(j)).Preferably, the elements M_(kj) may be selected to represent thechromaticity of the coordinates {A₁, . . . , A_(r)} in the primarycolors however, this is not required in order to display a balancedbrightness stereoscopic image. In general, the transformation M may be alinear transformation or it may a complex, non-linear function.

The linear brightness of the first image displayed in the primary colorsmay be approximated byY ^(L) P=Σ _(k)β_(k) P ^(L) _(k)=Σ_(k)β_(k) H _(P)(P _(k))where1=Σ_(k)β_(k).The parameters B_(k) may be determined from experimental observations ofthe relative brightness of the primary colors of the display apparatusviewed through a first viewing filter F₁.

In order to conserve the brightness contrast in the first image, theelements M_(kj) may satisfy the conditionα_(j)=λ₁Σ_(k)β_(k) M _(kj)where λ₁ is a scaling factor. These conditions may be satisfied byselecting elements M_(kj) which conserve the brightness of each initialcolor coordinate A_(j).

Third, the linear primary colors P^(L) _(k) may be transformed into thenon-linear values used by the display apparatusP _(k) =H ⁻¹ _(Pk)(P ^(L) _(k))where the functions H⁻¹ _(Pk) may be determined for the displayapparatus. A display apparatus may use a gamma function to approximateH_(Pk) as follows:P _(k)=(P ^(L) _(k))^(1/γ) ^(k)where the γ_(k) are properties of the display apparatus.

The transformation G₁ may be summarized asP _(k) =H ⁻¹ _(Pk)(Σ_(j) M _(kj) H _(Aj)(A _(j)))or sometimes asP _(k)=(Σ_(j) M _(kj) A ^(γ) _(j))^(1/γ) ^(k)where γ and γ_(k) are often near 2.2.

The above procedure may also be applied to the second image of a stereopair using the second filter F₂ to determine the brightness contributionof each primary color in the anaglyph image.

The transformation G₂ of the second image into the primary colors {Q₁, .. . , Q_(n)} which conserves the brightness contrast represented in thecoordinates {B₁, . . . , B_(s)} may be obtained as follows:

First, the coordinates {B₁, . . . , B_(s)} may be transformed intolinear brightness coordinates {B^(L) ₁, . . . , B^(L) _(s)}:B ^(L) _(j) =H _(Bj)(B _(j))using functions H_(Bj). The functions H⁻¹ _(Bj) are the non-linearityfunctions encoded into the coordinates of the second image.

In some reference color spaces, the form of the functions H_(Bj) may beapproximated by the gamma functions. For example in the sRGB colorspace, the functions H_(Bj) may be approximated by:H _(Bj)(B _(j))=B _(j) ^(γ) ^(j)where γj may be about 2.2. Then the linear brightness Y^(L) _(B) of thesecond image may be obtained by adding the contribution of eachcoordinate to the brightness:Y ^(L) _(B)=Σ_(j)δ_(j) B ^(L) _(j)where1=Σ_(j)δ_(j).The parameters δ_(j) may be determined from observations. In a referencecolor space, the values of δ_(j) may be known. For example in the sRGBcolor space, δ₁ may be about 0.2126, δ₂ may be about 0.7152, and δ₃ maybe about 0.0722.

Second, a transformation N may be selected to transform the coordinatesB^(L) _(j) into the linear primary color values Q^(L) _(k)=H_(Qk)(Q_(k))of the display apparatusQ ^(L) _(k)=Σ_(j) N _(kj) B ^(L) _(j)=Σ_(j) N _(kj) H _(Bj)(B _(j)).Preferably, the elements N_(kj) may be selected to represent thechromaticity of the coordinates {B₁, . . . , B_(s)} in the primarycolors {Q₁, . . . , Q_(n)} however, this is not required in order todisplay a balanced brightness stereoscopic image. In general,transformation N may be a linear transformation or it may a complex,non-linear function.

The linear brightness of the second image displayed in the primarycolors {Q₁, . . . , Q_(n)} may be approximated byY ^(L) _(Q)=Σ_(k)ε_(k) Q ^(L) _(k)=Σ_(k)ε_(k) H _(Qk)(Q _(k))where1=Σ_(k)ε_(k).The parameters ε_(k) may be determined from experimental observations ofthe relative brightness of the primary colors of the display apparatusviewed through a second viewing filter F₂.

In order to conserve the brightness contrast in the second image, theelements N_(kj) may satisfy the conditionδ_(j)=λ₂Σ_(k)ε_(k) N _(kj)where λ₂ is a scaling factor. This condition may be satisfied byselecting elements N_(kj) in order to conserve the brightness of eachinitial color coordinate B_(j).

Third, the linear primary colors Q^(L) _(k) may be transformed into thenon-linear values used by the display apparatusQ _(k) =H ⁻¹ _(Qk)(Q ^(L) _(k))where the functions H⁻¹ _(Qk) may be determined for the primary colorsof a display apparatus. A display apparatus may use a gamma function toapproximate the H_(Qk) as follows:Q _(k)=(Q ^(L) _(k))^(1/γ) ^(k)where the γ_(k) are properties of the display apparatus.

The transformation G₂ may be summarized asQ _(k) =H ⁻¹ _(Qk)(Σ_(j) N _(kj) H _(Bj)(B _(j)))or sometimes asQ _(k)=(Σ_(j) N _(kj) B ^(γ) _(j))^(1/γ) ^(k)where γ and γ_(k) are often near 2.2.

The filters F₁ and F₂ may be colored filters or polarized filters. Insome display methods, viewing filters may not be needed and the F₁ andF₂ filters may be replaced by the viewing apparatus of the displaymethod. If the spectra of the primary colors {P₁, . . . , P_(m)} do notsubstantially overlap the spectra of the primary colors {Q₁, . . . ,Q_(n)}, the viewing filters may be color filters where the first viewingfilter F₁ substantially transmits the primary colors {P₁, . . . , P_(m)}and blocks the primary colors {Q₁, . . . , Q_(n)}: and the secondviewing filter F₂ substantially transmits the primary colors {Q₁, . . ., Q_(n)} and blocks the primary colors {P₁, . . . , P_(m)}.

The two transformations G₁ and G₂ may be used to transform the initialstereoscopic image coordinates containing any distribution of color intodisplayed anaglyph images with balanced brightness contrast. Thesemethods apply to anaglyphs displayed using any number of primary colors.Examples of applying these transformations to various numbers of primarycolors are given below. Examples are described for two and three primarycolors {P₁, . . . , P_(m)} and one primary color {Q₁} corresponding tothree-color and four-color anaglyphs. Examples are described for two andthree primary colors {Q₁, . . . , Q_(n)} corresponding to five-color andsix-color anaglyphs.

Balanced Brightness Three Primary Color Anaglyphs

An example of applying transformations G₁ and G₂ to the case of a threeprimary color anaglyph follows:

For this example, the first image may be stored in red R₁, G₁ and blueB₁ coordinates of the sRGB color space and displayed in primary colorsgreen G_(a), and blue B_(a) of a display apparatus. The brightnesscontributions of the red R₁, green G₁ and blue B₁ coordinates of thesRGB color space may be approximated byY ^(L) _(A)=0.2126R ^(L) ₁+0.7152G ^(L) ₁+0.0722B ^(L) ₁where a gamma function may be used to linearize the image coordinatesR ^(L) ₁ =R ₁ ^(γ),G ^(L) ₁ =G ₁ ^(γ), andB ^(L) ₁ =B ₁ ^(γ)where γ may be about 2.2.

For a particular cyan color filter F₁ and a particular displayapparatus, the green primary color G^(L) ₁ may contribute about 80percent to the brightness while the blue primary color B^(L) ₁ maycontribute about 20 percent to the brightnessY ^(L) _(P)=0.80G ^(L) _(a)+0.20B ^(L) _(a).The balanced brightness conditions on the transformation M_(kj) may be0.21=0.80M _(GR)+0.20M _(BR),0.72=0.80M _(GG)+0.20M _(BG),0.07=0.80M _(GB)+0.20M _(BB).

The coordinate G^(L) ₁ may be mapped 100 percent into the primary colorG^(L) _(a). The coordinate B^(L) ₁ may be mapped 100 percent into theprimary color B^(L) _(a). The coordinate R^(L) ₁ may be mapped 50percent into the primary color G^(L) _(a) and 50 percent into theprimary color B^(L) _(a). In other words, M_(BG)=M_(GB)=0 andM_(GR)=M_(BR). This choice maps the coordinate R^(L) ₁ into a cyan orgray color of the anaglyph. Then0.21=0.80M _(GR)+0.20M _(BR),0.72=0.80M _(GG),0.07=0.20M _(BB).It follows that M_(GR)=M_(BR)=0.21, M_(GG)=0.9, and M_(GB)=0.35. ThenG ^(L) _(a)=0.9G ^(L) ₁+0.21R ^(L) ₁,B ^(L) _(a)=0.35B ^(L) ₁+0.21R ^(L) ₁.Since M_(GG)+M_(GR)=1.11, is greater than 1.0, the values of G^(L) _(a)may exceed the capabilities of the display apparatus. Therefore, theM_(kj) may be divided by 1.11 to obtainG ^(L) _(a)=0.81G ^(L) ₁+0.19R ^(L) ₁,B ^(L) _(a)=0.32B ^(L) ₁+0.19R ^(L) ₁.The renormalization of the M_(kj) elements will be understood by thoseskilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₁ may be written as:G _(a)=(0.81G ₁ ^(γ)+0.19R ₁ ^(γ))^(1/γ),B _(a)=(0.32B ₁ ^(γ)+0.19R ₁ ^(γ))^(1/γ)where in this case γ may be taken to be 2.2. Here the coordinate R₁ addsequally to the primary colors G_(a) and B_(a) which contributes to the“grayscale” level the anaglyph. Other choices of M may be used to shiftthe contribution of R₁ toward either the green or blue channels.

The second image may be stored in red R₂, G₂ and blue B₂ coordinates ofthe sRGB color space and displayed in a red primary color R_(a) of adisplay apparatus. The brightness contributions of the red R₂, green G₂and blue B₂ coordinates of the sRGB color space may be approximated byY ^(L) _(B)=0.2126R ^(L) ₂+0.7152G ^(L) ₂+0.0722B ^(L) ₂where a gamma function may be used to linearize the image coordinatesR ^(L) ₂ =R ₂ ^(γ),G ^(L) ₂ =G ₂ ^(γ), andB ^(L) ₂ =B ₂ ^(γ)where γ may be about 2.2.

For a particular color filter F₂, the primary color R^(L) _(a) maycontribute 100 percent to the brightness of the displayed second image.Y ^(L) _(Q)=1.0R ^(L) _(a).The red R^(L) ₂, green G^(L) ₂ and blue B^(L) ₂ coordinates may bemapped 100 percent into the primary color R^(L) _(a). The balancedbrightness conditions on the transformation N_(kj) may be0.21=N _(RR),0.72=N _(RG),0.07=N _(RB).ThenR ^(L) _(a)=0.21R ^(L) ₂+0.72G ^(L) ₂+0.07B ^(L) ₂.The complete transformation G₂ may be written as:R _(a)=(0.21R ₂ ^(γ)+0.72G ₂ ^(γ)+0.07B ₁ ^(γ))^(1/γ)where in this case γ may be taken to be 2.2.

These transformations G₁ and G₂ may be used to create balancedbrightness anaglyphs with three primary colors from stereoscopic imageswith any initial color distribution once the calibration parameters aredetermined accurately. Although this example is applied to a red/cyananaglyph, the methods of the present invention may also be applied toblue/yellow and green/magenta anaglyphs.

Balanced Brightness Four Primary Color Anaglyphs

An example of applying transformations G₁ and G₂ to the case of a fourprimary color anaglyph follows:

For this example, the first image may be stored in red R₁, G₁ and blueB₁ coordinates of the sRGB color space and displayed in primary colorsred R_(a), green G_(a), and blue B_(a) of a display apparatus. Thebrightness contributions of the red R₁, green G₁ and blue B₁ coordinatesof the sRGB color space may be approximated byY ^(L) _(A)=0.2126R ^(L) ₁+0.7152G ^(L) ₁+0.0722B ^(L) ₁where a gamma correction may be used to linearize the image coordinatesR ^(L) ₁ =R ₁ ^(γ),G ^(L) ₁ =G ₁ ^(γ), andB ^(L) ₁ =B ₁ ^(γ)where γ may be about 2.2.

For a particular color filter F₁ and a particular display apparatus, thered primary color R^(L) ₁ may contribute about 30 percent to thebrightness, the green primary color G^(L) ₁ may contribute about 60percent to the brightness, while the blue primary color B^(L) ₁ maycontribute about 10 percent to the brightnessY ^(L) _(P)=0.30R ^(L) ₁+0.60G ^(L) ₁+0.10B ^(L) ₁.The balanced brightness conditions on the transformation M_(kj) may be0.21=0.30M _(RR)+0.60M _(GR)+0.10M _(BR),0.72=0.30M _(RG)+0.60M _(GG)+0.10M _(BG),0.07=0.30M _(RB)+0.60M _(GB)+0.10M _(BB).A simple case is to set the off diagonal elements of M_(kj) to zero.Then0.21=0.30M _(RR),0.72=0.60M _(GG),0.07=0.10M _(BB).It follows that M_(RR)=0.7, M_(GG)=1.2, and M_(BB)=0.7. ThenR ^(L) _(a)=0.7R ^(L) ₁,G ^(L) _(a)=1.2G ^(L) ₁,B ^(L) _(a)=0.7B ^(L) ₁.

Since M_(GG)=1.2, is greater than 1.0, the values of G^(L) _(a) mayexceed the capabilities of the display apparatus. Therefore, the M_(kj)may be divided by 1.2 to obtainR ^(L) _(a)=0.58R ^(L) ₁,G ^(L) _(a)=1.0G ^(L) ₁,B ^(L) _(a)=0.58B ^(L) ₁.The renormalization of the elements of M_(kj) will be understood bythose skilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₁ may be written as:R ^(L) _(a)=(0.58R ₁ ^(2.2))^(1/γ),G ^(L) _(a) =G ₁ ^(2.2/γ),B ^(L) _(a)=(0.58B ₁ ^(2.2))^(1/γ)where γ_(j) may often be chosen to be 2.2 for each primary color P_(j),but this may depend on the properties of the primary colors of thedisplay apparatus. If γ=2.2, thenR _(a)=0.78R _(1,)G _(a) =G ₁,B _(a)=0.78B ₁.

In general, a transformation G₁ may also be selected to map thechromaticity of the first image in the primary colors {P₁, P₂, P₃} tothe chromaticity of the first image in the coordinates {A₁, . . . ,A_(m)}. In this case, the off-diagonal elements of M_(kj) may notnecessarily be zero and the transformation M_(kj) may be more complex.

The second image may be stored in red R₂, green G₂, and blue B₂coordinates of the sRGB color space and displayed in a fourth primarycolor Q₁ of a display apparatus. The brightness contributions of the redR₂, green G₂ and blue B₂ coordinates of the sRGB color space may beapproximated byY ^(L) _(B)=0.2126R ^(L) ₂+0.7152G ^(L) ₂+0.0722B ^(L) ₂where a gamma correction may be used to linearize the image coordinatesR ^(L) ₂ =R ₂ ^(γ),G ^(L) ₂ =G ₂ ^(γ), andB ^(L) ₂ =B ₂ ^(γ)where γ may be about 2.2.

For a particular color filter F₂, the primary color Q^(L) ₁ maycontribute 100 percent to the brightness of the displayed second image.Y ^(L) _(Q)=1.0Q ^(L) ₁.The red R^(L) ₂, green G^(L) ₂ and blue B^(L) ₂ coordinates may bemapped 100 percent into the primary color Q^(L) ₁. The balancedbrightness conditions on the transformation N_(kj) may be0.21=N _(RR),0.72=N _(RG),0.07=N _(RB).ThenQ ^(L) ₁=0.21R ^(L) ₂+0.72G ^(L) ₂+0.07B ^(L) ₂.The complete transformation G₂ may be written as:Q ₁=(0.21R ₂ ^(γ)+0.72G ₂ ^(γ)+0.07B ₂ ^(γ))^(1/γ)where in this case γ may be taken to be 2.2.

These transformations G₁ and G₂ may be used to create balancedbrightness anaglyphs with four primary colors from stereoscopic imageswith any initial color distribution once the calibration parameters aredetermined accurately.

Balanced Brightness Five Primary Color Anaglyphs

An example of applying transformations G₁ and G₂ to the case of fiveprimary color anaglyphs follows:

For this example, the first image may be stored in red R₁, green G₁, andblue B₁ coordinates of the sRGB color space and displayed in primarycolors red R_(a), green G_(a), and blue B_(a) of a display apparatus.The brightness contributions of the red R₁, green G₁ and blue B₁coordinates of the sRGB color space may be approximated byY ^(L) _(A)=0.2126R ^(L) ₁+0.7152G ^(L) ₁+0.0722B ^(L) ₁where a gamma correction may be used to linearize the image coordinatesR ^(L) ₁ =R ₁ ^(γ),G ^(L) ₁ =G ₁ ^(γ), andB ^(L) ₁ =B ₁ ^(γ)where γ may be about 2.2.

For a particular color filter F₁ and a particular display apparatus, thered primary color R^(L) ₁ may contribute about 30 percent to thebrightness the green primary color G^(L) ₁ may contribute about 60percent to the brightness while the blue primary color B^(L) ₁ maycontribute about 10 percent to the brightnessY ^(L) _(P)=0.30R ^(L) ₁+0.60G ^(L) ₁+0.10B ^(L) ₁.The balanced brightness conditions on the transformation M_(kj) may be0.21=0.30M _(RR)+0.60M _(GR)+0.10M _(BR),0.72=0.30M _(RG)+0.60M _(GG)+0.10M _(BG),0.07=0.30M _(RB)+0.60M _(G) B+0.10M _(BB).A simple case is to set the off diagonal elements of M_(kj) to zero.Then0.21=0.30M _(RR),0.72=0.60M _(GG),0.07=0.10M _(BB).It follows that M_(RR)=0.7, M_(GG)=1.2, and M_(BB)=0.7. ThenR ^(L) _(a)=0.7R ^(L) ₁,G ^(L) _(a)=1.2G ^(L) ₁,B ^(L) _(a)=0.7B ^(L) ₁.

Since M_(GG)=1.2, is greater than 1.0, the values of G^(L) _(a) mayexceed the capabilities of the display apparatus. Therefore, the M_(kj)may be divided by 1.2 to obtainR ^(L) _(a)=0.58R ^(L) ₁,G ^(L) _(a)=1.0G ^(L) ₁,B ^(L) _(a)=0.58B ^(L) ₁.The renormalization of the elements of M_(kj) will be understood bythose skilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₁ may be written as:R ^(L) _(a)=(0.58R ₁ ^(2.2))^(1/γ),G ^(L) _(a) =G ₁ ^(2.2/γ)B ^(L) _(a)=(0.58B ₁ ^(2.2))^(1/γ)where the γ_(j) may often be chosen to be 2.2 for each primary colorP_(j), but this may depend on the properties of the primary colors ofthe display apparatus. If γ=2.2, thenR _(a)=0.78R ₁,G _(a) =G ₁,B _(a)=0.78B ₁.

In general, a transformation G₁ may also be selected to map thechromaticity of the first image in the primary colors {P₁, P₂, P₃} tothe chromaticity of the first image in the coordinates {A₁, . . . ,A_(m)}. In this case, the off-diagonal elements of M_(kj) may notnecessarily be zero and the transformation M_(kj) may be more complex.

The second image may be stored in red R₂, green G₂ and blue B₂coordinates of the sRGB color space and displayed in a fourth and fifthprimary colors primary color {Q₁, Q₂} of a display apparatus. Thebrightness contributions of the red R₂, green G₂ and blue B₂ coordinatesof the sRGB color space may be approximated byY ^(L) _(B)=0.2126R ^(L) ₂+0.7152G ^(L) ₂+0.0722B ^(L) ₂where a gamma correction may be used to linearize the image coordinatesR ^(L) ₂ =R ₂ ^(γ),G ^(L) ₂ =G ₂ ^(γ), andB ^(L) ₂ =B ₂ ^(γ)where γ may be about 2.2.

For this example, the primary color Q₁ may be a red and the primarycolor Q₂ may be a cyan. For a particular color filter F₂, the primarycolor Q^(L) ₁ may contribute 50 percent to the brightness while theprimary color Q^(L) ₂ may contribute 50 percent to the brightness of thedisplayed second imageY ^(L) _(Q)=0.5Q ^(L) ₁+0.5Q ^(L) ₂

The red coordinate R^(L) ₂, may be mapped 100 percent into the primarycolor Q^(L) ₁. The green coordinate G^(L) ₂, may be mapped 50 percentinto the primary color Q^(L) ₁ and 50 percent into the primary colorQ^(L) ₂. The blue coordinate B^(L) ₂, may be mapped 100 percent into theprimary color Q^(L) ₂. In other words, N_(2R)=N_(1B)=0 andN_(1G)=N_(2G).

The balanced brightness conditions on the transformation N_(kj) may be0.21=0.50N _(1R),0.72=0.50N _(1G)+0.50N _(2G),0.07=0.50N _(2B).It follows that N_(1R)=0.42, N_(1G)=N_(2G)=0.72, and M_(2B)=0.14. ThenQ ^(L) ₁=0.42R ^(L) ₂+0.72G ^(L) ₂,Q ^(L) ₂=0.72G ^(L) ₂+0.14B ^(L) ₂.

Since N_(1R)+N_(1G)=1.14, is greater than 1.0, the values of Q^(L) ₁ mayexceed the capabilities of the display apparatus. Therefore, the N_(kj)may be divided by 1.14 to obtainQ ^(L) ₁=0.37R ^(L) ₂+0.63G ^(L) ₂,Q ^(L) ₂=0.63G ^(L) ₂+0.12B ^(L) ₂.The renormalization of the N_(kj) elements will be understood by thoseskilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₂ may be written as:Q ₁=(0.37R ₂ ^(γ)+0.63G ₂ ^(γ))^(1/γ),Q ₂=(0.63G ₂ ^(γ)+0.12B ₂ ^(γ))^(1/γ)where in this case γ may be taken to be 2.2.

These transformations G₁ and G₂ may be used to create balancedbrightness anaglyphs with five primary colors from stereoscopic imageswith any initial color distribution once the calibration parameters aredetermined accurately.

Balanced Brightness Six Primary Color Anaglyphs

An example of applying transformations G₁ and G₂ to the case of a sixprimary color anaglyph follows:

For this example, the first image may be stored in red R₁, green G₁ andblue B₁ coordinates of the sRGB color space and displayed in primarycolors red P₁, green P₂, and blue P₃ of a display apparatus. Thebrightness contributions of the red R₁, green G₁ and blue B₁ coordinatesof the sRGB color space may be approximated byY ^(L) _(A)=0.2126R ^(L) ₁+0.7152G ^(L) ₁+0.0722B ^(L) ₁where a gamma correction may be used to linearize the image coordinatesR ^(L) ₁ =R ₁ ^(γ),G ^(L) ₁ =G ₁ ^(γ), andB ^(L) ₁ =B ₁ ^(γ)where γ may be about 2.2.

For a particular color filter F₁ and a particular display apparatus, thered primary color R^(L) ₁ may contribute about 25 percent to thebrightness, the green primary color G^(L) ₁ may contribute about 70percent to the brightness, while the blue primary color B^(L) ₁ maycontribute about 5 percent to the brightnessY ^(L) _(P)=0.25P ^(L) ₁+0.70P ^(L) ₂+0.05P ^(L) ₃.The balanced brightness conditions on the transformation M_(kj) may be0.21=0.25M _(1R)+0.70M _(2R)+0.05M _(3R),0.72=0.25M _(1G)+0.70M _(2G)+0.05M _(3G),0.07=0.25M _(1B)+0.70M _(2B)+0.05M _(3B).A simple case is to set the off diagonal elements of M_(kj) to zero.Then0.21=0.25M _(1R),0.72=0.70M _(2G),0.07=0.05M _(3B).It follows that M_(1R)=0.84, M_(2G)=1.03, and M_(3B)=1.4. ThenP ^(L) ₁=0.84R ^(L) ₁,P ^(L) ₂=1.03G ^(L) ₁,P ^(L) ₃=1.4B ^(L) ₁.Since M_(3B)=1.4, is greater than 1.0, the values of P^(L) ₃ may exceedthe capabilities of the display apparatus. Therefore, the M_(kj) may bedivided by 1.4 to obtainP ^(L) ₁=0.60R ^(L) ₁,P ^(L) ₂=0.74G ^(L) ₁,P ^(L) ₃=1.00B ^(L) ₁.The renormalization of the elements of M_(kj) will be understood bythose skilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₁ may be written as:P ^(L) ₁=(0.60R ₁ ^(2.2))^(1/γ),P ^(L) ₂=(0.74G ₁ ^(2.2))^(1/γ),P ^(L) ₃=(1.00B ₁ ^(2.2))^(1/γ)where γ may often be chosen to be identical for each primary colorP_(j), but this may depend on the properties of the primary colors ofthe display apparatus. If γ=2.2, thenP ₁=0.79R ₁,P ₂=0.87G ₁,P ₂=1.00B ₁.

In general, a transformation G₁ may also be selected to map thechromaticity of the first image in the primary colors {P₁, P₂, P₃} tothe chromaticity of the first image in the coordinates {A₁, . . . ,A_(m)}. In this case, the off-diagonal elements of M_(kj) may notnecessarily be zero and the transformation may be more complex.

The second image may be stored in red R₂, green G₂ and blue B₂coordinates of the sRGB color space and displayed in fourth, fifth andsixth primary colors {Q₁, Q₂, Q₃} of a display apparatus. The brightnesscontributions of the red R₂, green G₂ and blue B₂ coordinates of thesRGB color space may be approximated byY ^(L) _(B)=0.2126R ^(L) ₂+0.7152G ^(L) ₂+0.0722B ^(L) ₂where a gamma correction may be used to linearize the image coordinatesR ^(L) ₂ =R ₂ ^(γ),G ^(L) ₂ =G ₂ ^(γ), andB ^(L) ₂ =B ₂ ^(γ)where γ may be about 2.2.

For this example, the primary color Q₁ may be red, the primary color Q₂may be a green, and the primary color Q₂ may be blue. For a particularcolor filter F₂, the primary color Q^(L) ₁ may contribute 15 percent tothe brightness, the primary color Q^(L) ₂ may contribute 70 percent tothe brightness, and the primary color Q^(L) ₃ may contribute 15 percentto the brightness of the displayed second imageY ^(L) _(Q)=0.15Q ^(L) ₁+0.70Q ^(L) ₂+0.15Q ^(L) ₃

The red coordinate R^(L) ₂, may be mapped 100 percent into the primarycolor Q^(L) ₁. The green coordinate G^(L) ₂, may be mapped 100 percentinto the primary color Q^(L) ₂. The blue coordinate B^(L) ₂, may bemapped 100 percent into the primary color Q^(L) ₃. In this case, theoff-diagonal elements of N_(jk) may be zero.

The balanced brightness conditions on the transformation N_(kj) may be0.21=0.15N _(1R),0.72=0.70N _(2G),0.07=0.15N _(3B).It follows that N_(1R)=1.40, N_(2G)=1.03, and M_(2B)=0.47. ThenQ ^(L) ₁=1.40R ^(L) ₂,Q ^(L) ₂=1.03G ^(L) ₂,Q ^(L) ₃=0.47B ^(L) ₂.Since N_(1R)=1.40, is greater than 1.0, the values of Q^(L) ₁ may exceedthe capabilities of the display apparatus. Therefore, the N_(kj) may bedivided by 1.14 to obtainQ ^(L) ₁=1.00R ^(L) ₂,Q ^(L) ₂=0.73G ^(L) ₂,Q ^(L) ₃=0.34B ^(L) ₂.The renormalization of the N_(kj) elements will be understood by thoseskilled in the art to be consistent with balancing the brightnesscontrast of the displayed images.

The complete transformation G₂ may be written as:Q ₁=(1.00R ₂ ^(2.2))^(1/γ),Q ₂=(0.73G ₂ ^(2.2))^(1/γ),Q ₃=(0.34B ₂ ²⁻²)^(1/γ).where γ_(j) may often be chosen to be identical for each primary colorQ_(j), but this may depend on the properties of the primary colors ofthe display apparatus. If γ=2.2, thenQ ₁=1.00R ₂,Q ₂=0.87G ₂,Q ₃=0.61B ₂.

These transformations G₁ and G₂ may be used to create balancedbrightness anaglyphs with six primary colors from stereoscopic imageswith any distribution of color once the calibration parameters aredetermined accurately.

The above examples involved images represented in the sRGB color space.The methods of the present invention also apply to images represented inother color spaces such as the CIE xyY, CIE XYZ and other color spaces.

Primary Colors of Generalized Anaglyphs

Another embodiment of the present invention provides methods to displayanaglyphs using only one primary color {Q₁} to display the second imageand primary colors {P₁, . . . , P_(m)} to display the first image andwith balanced brightness contrast in the first and second images. Theseanaglyphs may have a color gamut which may be substantially identical tothe color gamut of the primary colors {P₁, . . . , P_(m)} of the firstimage viewed through the first viewing filter F₁. Herein, the colorgamut of an image is defined to be the color gamut of the primary colorsused to display the image. The color gamut of a set of primary colors isthe set of colors which may be displayed by combining the primary colorsin various ratios. A color gamut is often defined by the set of pointsin a CIE xy chromaticity diagram which is bounded by the outer polygonwhich connects the points in the diagram which represent the primarycolors. Anaglyphs displayed using three primary colors and with balancedbrightness contrast in the first and second images may have a reducedcolor gamut substantially defined by just two primary colors {P₁, P₂}.Anaglyphs displayed using four (or more) primary colors and withbalanced brightness contrast in the first and second images may have afull color gamut substantially defined by three primary colors {P₁, P₂,P₃}. Herein a full-color gamut is a color gamut in which comprises thesix hues red, yellow, green, cyan, blue, and magenta. A four-coloranaglyph of the present invention with balanced brightness contrast mayinclude a primary color {Q₁} that is red, yellow, green, cyan, blue,magenta or white. The case of a white primary color {Q₁} is discussedfurther herein.

FIG. 1 a depicts the spectra of three primary colors green P₁, blue P₂,and red Q₁ of a three-color anaglyph. FIG. 1 a also depicts the spectra122 of a first viewing filter F₁ and a second viewing filter F₂ forviewing a red/cyan anaglyph. The first filter F₁ substantially transmitsthe green and blue primary colors and blocks the red primary color. Thesecond filter F₂ substantially transmits the red primary color andblocks the green and blue primary colors. FIG. 1 b depicts the red Q₁,green P₁, and blue P₂ primary colors in a CIE xy chromaticity diagram.The color gamut of a red/cyan anaglyph displayed with these primarycolors and viewed through filters F₁ and F₂ may be substantially thecolor gamut of the green P₁ and blue P₂ primary colors viewed throughthe first filter F₁. The color gamut of the first image or of thered/cyan anaglyph is depicted in FIG. 1 b by the line segment 132connecting the green P₁ and blue P₂ primary colors. The color gamut mayinclude yellowish-green, unsaturated green, and blue hues. The hues nearcyan may become desaturated due to the shift of the white point W_(p)′toward the cyan hue when viewing through a cyan filter compared with theconventional white point W_(p). Three-color anaglyphs of the presentembodiment have the advantage of being compatible with many displayapparatus, may have negligible retinal rivalry, but have thedisadvantage of having a reduced color gamut. Similar three-coloranaglyphs of the present invention may include blue/yellow anaglyphs andgreen/magenta anaglyphs with balanced brightness contrast in the firstand second images.

FIG. 2 a depicts the spectra of four primary colors red P₁, green P₂,blue P₃, and yellow Q₁ of a four-color (yellow/RGB) anaglyph. FIG. 2 aalso depicts the spectra 222 of a first viewing filter F₁ and a secondviewing filter F₂ for viewing a yellow/RGB anaglyph. The first filter F₁substantially transmits the red, green and blue primary colors andblocks the yellow primary color. The second filter F₂ substantiallytransmits the yellow primary color and blocks the red, green and blueprimary colors. FIG. 2 b depicts the red P₁, green P₂, blue P₃, andyellow Q₁ primary colors in a CIE xy chromaticity diagram. The colorgamut of a yellow/RGB anaglyph displayed with these primary colors andviewed through filters F₁ and F₂ may be substantially the color gamut ofthe red P₁, green P₂, and blue P₃ primary colors viewed through thefirst filter F₁. The color gamut of the first image or of the yellow/RGBanaglyph is depicted in FIG. 2 b by the triangle 232 connecting the redP₁, green P₂, and blue P₃ primary colors. The color gamut may be a fullcolor gamut comprising the six hues red, yellow, green, cyan, blue, andmagenta. Four-color anaglyphs have the advantage of providing a fullcolor gamut, may have negligible retinal rivalry, while being relativelysimple to implement in a display apparatus. Similar four-color anaglyphsof the present invention may include a primary color Q₁ which may bered, yellow, green, cyan, blue, magenta and white.

Another embodiment of the present invention provides methods to displayanaglyphs using three primary colors {P₁, P₂, P₃} to display the firstimage and three primary colors {Q₁, Q₂, Q₃} to display the second imageand with balanced brightness contrast in the first and second images.These anaglyphs may have a color gamut which is substantially acombination of the color gamut of the primary colors {P₁, P₂, P₃} of thefirst image viewed through the first viewing filter F₁ and the colorgamut of the primary colors {Q₁, Q₂, Q₃} of the second image viewedthrough the second viewing filter F₂. Since the color gamuts of thefirst and second images may be full-color gamuts, the combined colorgamuts of the anaglyph may also be a full-color gamut.

FIG. 3 a depicts the spectra of six primary colors red P₁, green P₂,blue P₃, red Q₁, green Q₂, and blue Q₃ of a six-color (RGB/RGB)anaglyph. FIG. 3 a also depicts the spectra 322 of the first viewingfilter F₁ and a second viewing filter F₂ for viewing a RGB/RGB anaglyph.The first filter F₁ substantially transmits the red P₁, green P₂, andblue P₃ primary colors and blocks the red Q₁, green Q₂, and blue Q₃primary colors. The second filter F₂ substantially transmits the red Q₁,green Q₂, and blue Q₃ primary colors and blocks the red P₁, green P₂,and blue P₃ primary colors. FIG. 3 b depicts the red P₁, green P₂, blueP₃, red Q₁, green Q₂, and blue Q₃ primary colors in a CIE xychromaticity diagram. The color gamut of a RGB/RGB anaglyph displayedwith these primary colors and viewed through filters F₁ and F₂ may besubstantially a weighted average of the color gamut of the red P₁, greenP₂, and blue P₃ primary colors viewed through the first filter F₁ andthe color gamut of the red Q₁, green Q₂, and blue Q₃ primary colorsviewed through the second filter F₂. The color gamut of a first image isdepicted in FIG. 4 c by the triangle 332 connecting the red 1, green 2and blue 3 primary colors. The color gamut of a second image is depictedin FIG. 3 b by the triangle 334 connecting the red 11, green 12 and blue13 primary colors. The color gamut of the anaglyph may be a full-colorgamut comprising the six hues red, yellow, green, cyan, blue, andmagenta.

Six-color anaglyphs have the advantage of providing a full color gamutwhile being relatively simple to implement in a display apparatus.However, six-color primary color anaglyphs of the prior art requirefilters F₁ and F₂ with spectra which may be difficult or expensive tomanufacture. Also six-color anaglyphs may be substantially less brightthan single images displayed with a similar display apparatus (forexample a display apparatus with a similar lumens output). Othersix-color anaglyphs of the present invention are discussed herein.

Another embodiment of the present invention provides methods to displayanaglyphs using three primary colors {P₁, P₂, P₃} to display the firstimage and three primary colors {Q₁, Q₂, Q₃} to display the second imagewhere the order of the primary colors in a spectral scale may be (Q₁,P₁, P₂, Q₂, Q₃, P₃) or (Q₁, P₁, P₂, Q₂, P₃, Q₃) or (P₁, Q₁, P₂, Q₂, Q₃,P₃). Herein the notation associated with the term spectral scale impliesthat the wavelengths λ_(k) of the light of the primary color X_(k)substantially satisfy the relation λ₁>λ_(j)>λ_(m). These anaglyphs mayhave a color gamut which is substantially a weighted average of thecolor gamut of the primary colors {P₁, P₂, P₃} of the first image viewedthrough the first viewing filter F₁ and the color gamut of the primarycolors {Q₁, Q₂, Q₃} of the second image viewed through the secondviewing filter F₂. Since the color gamuts of the first and second imagesmay be full-color gamuts, the combined color gamuts of the anaglyph mayalso be a full-color gamut. The spectra of the viewing filters F₁ and F₂for viewing these anaglyphs may be manufactured more easily or lessexpensively than the viewing filters for the six-color anaglyphs of theprior art.

FIG. 4 a depicts the spectra of six primary colors red P₁, green P₂,blue P₃, red Q₁, green Q₂, and blue Q₃ of a six-color {RGB/RGB) anaglyphwith spectral order (Q₁, P₁, P₂, Q₂, Q₃, P₃). FIG. 4 a also depicts thespectra 422 of a first viewing filter F₁ and a second viewing filter F₂for viewing the RGB/RGB anaglyph. The first filter F₁ substantiallytransmits the red P₁, green P₂, and blue P₃ primary colors and blocksthe red Q₁, green Q₂, and blue Q₃ primary colors. The second filter F₂substantially transmits the red Q₁, green Q₂, and blue Q₃ primary colorsand blocks the red P₁, green P₂, and blue P₃ primary colors. FIG. 4 bdepicts the red P₁, green P₂, blue P₃, red Q₁, green Q₂, and blue Q₃primary colors in a CIE xy chromaticity diagram. The color gamut of aRGB/RGB anaglyph displayed with these primary colors and viewed throughfilters F₁ and F₂ may be substantially a weighted average of the colorgamut of the red P₁, green P₂, and blue P₃ primary colors viewed throughthe first filter F₁ and the red Q₁, green Q₂, and blue Q₃ primary colorsviewed through the second filter F₂. The color gamut of a first image isdepicted in FIG. 4 b by the triangle 432 connecting the red P₁, greenP₂, and blue P₃ primary colors. The color gamut of a second image isdepicted in FIG. 4 b by the triangle 434 connecting the red Q₁, green Q₂and blue Q₃ primary colors. The color gamut of the anaglyph may be afull-color gamut comprising the six hues red, yellow, green, cyan, blue,and magenta. An advantage of the present embodiment over the six-coloranaglyphs of the prior art is that the spectra of the viewing filters F₁and F₂ may be simpler and less expensive to manufacture.

A display apparatus that provides six primary colors to display twoimages is often less than half as bright as a similar display apparatuswhich displays just one image. On the other hand, a display apparatuswith four primary colors may display the first image at nearly the fullbrightness of the display apparatus using three primary colors whileusing the fourth primary color to display the second image. The secondimage may be displayed at about 10-30% of the brightness of the firstimage while providing a comfortable stereo view to the users.Furthermore in a four-color anaglyph, the primary color Q₁ may becomposed of light in regions of the visible spectrum which is not fullyused in the primary colors {P₁, . . . , P_(m)} which further increasesthe brightness of the anaglyph images. However, the color gamut of afour-color anaglyph may be affected by the second monochrome image inregions of a stereoscopic image where the color of the first image isunsaturated. In other words, the white colors of the stereo view may beperceived to have a tint associated with the primary color Q₁ of thesecond image. An anaglyph displayed with five primary colors may improvethe white colors of the stereo view compared with the white colors offour-color anaglyphs while requiring viewing filters which may be lessexpensive to manufacture than the viewing filters for six-coloranaglyphs.

Another embodiment of the present invention provides methods to displayanaglyphs using primary colors {P₁, . . . , P_(m)} to display the firstimage and two primary colors {Q₁, Q₂} to display the second image. Theseanaglyphs may have a color gamut which is a weighted average of thecolor gamut of the primary colors {P₁, . . . , P_(m)} of the first imageviewed through the first viewing filter F₁ and the color gamut of theprimary colors {Q₁, Q₂} of the second image viewed through the secondviewing filter F₂. If the first image is displayed in three primarycolors {P₁, P₂, P₃}, the color gamut of the first image may be fullcolor. The color gamut of the second image may be a reduced color gamutincluding up to three color hues in the set {red, yellow, green, cyan,blue, and magenta}. The primary colors {Q₁, Q₂} may be chosen so thatthe most important hues may be included in the color gamut of the secondimage. The color gamut of the anaglyph may include the hues which may beincluded in either color gamuts of the first and second images. Howeverthe hues which may be included in the color gamuts of only one of thefirst and second images may appear in the color gamut of the anaglyph atreduced saturation or with a shift in perceived hue. The colors of thesecond image may be rendered in hues which most closely correspond tothe hue in the first image or rendered as a desaturated hue. If thesecond image is displayed with less brightness than the first image, thecolor gamut of the anaglyph may be closer to the color gamut of thefirst image than the color gamut of the second image.

FIG. 5 a depicts the spectra of five primary colors red P₁, green P₂,blue P₃, yellow Q₁, and blue Q₂ of a five-color (YB/RGB) anaglyph havinga spectral order (P₁, Q₁, P₂, Q₂, P₃). FIG. 5 a also depicts the spectra522 of the first viewing filter F₁ and a second viewing filter F₂ forviewing a YB/RGB anaglyph. The first filter F₁ substantially transmitsthe red P₁, green P₂, and blue P₃ primary colors and blocks the yellowQ₁ and blue Q₂ primary colors. The second filter F₂ substantiallytransmits the yellow Q₁ and blue Q₂ primary colors and blocks the redP₁, green P₂, and blue P₃ primary colors. FIG. 5 b depicts the red P₁,green P₂, blue P₃, yellow Q₁, and blue Q₂ primary colors in a CIE xychromaticity diagram. The color gamut of a YB/RGB anaglyph displayedwith these primary colors and viewed through filters F₁ and F₂ may besubstantially a weighted average of the color gamut of the red P₁, greenP₂, and blue P₃ primary colors viewed through the first filter F₁ andthe color gamut of the yellow Q₁ and blue Q₂ primary colors viewedthrough the second filter F₂. The color gamut of a first image isdepicted in FIG. 5 b by the triangle 532 connecting the red P₁, green P₂and blue P₃ primary colors. The color gamut of a second image isdepicted in FIG. 5 b by the line segment 534 connecting the yellow Q₁and blue Q₂ primary colors. The color gamut of the anaglyph may be afull color gamut comprising the six hues red, yellow, green, cyan, blue,and magenta. The green hues of the second image may be rendered aseither yellow, yellowish green, nearly white or blue. This may produceyellowish-green or desaturated green hues in the color gamut of theanaglyph. Red hues of the second image may be rendered as either yellowor unsaturated yellow or nearly white. This may produce reddish-orangeor desaturated green hues in the color gamut of the anaglyph. Blue huesof the second image may be rendered as either blue or nearly white. Thismay produce blue hues in the color gamut of the anaglyph. Yellow andcyan hues of the second image may be rendered as yellow and blue huesproducing yellow and cyan hues in the color gamut of the anaglyph.Magenta hues of the second image may be rendered as nearly white huesproducing desaturated magenta hues in the color gamut of the anaglyph.

FIG. 6 a depicts the spectra of five primary colors red P₁, green P₂,blue P₃, far-red Q₁, and cyan Q₂ of a five-color (RC/RGB) anaglyphhaving a spectral order (Q₁, P₁, P₂, Q₂, P₃). FIG. 6 a also depicts thespectra 622 of a first viewing filter F₁ and a second viewing filter F₂for viewing a RC/RGB anaglyph. The first filter F₁ substantiallytransmits the red P₁, green P₂, and blue P₃ primary colors and blocksthe far-red Q₁ and cyan Q₂ primary colors. The second filter F₂substantially transmits the far-red Q₁ and cyan Q₂ primary colors andblocks the red P₁, green P₂, and blue P₃ primary colors. FIG. 6 bdepicts the red P₁, green P₂, blue P₃, far-red Q₁, and cyan Q₂ primarycolors in a CIE xy chromaticity diagram. The color gamut of a RC/RGBanaglyph displayed with these primary colors and viewed through filtersF₁ and F₂ may be substantially a weighted average of the color gamut ofthe red P₁, green P₂, and blue P₃ primary colors viewed through thefirst filter F₁ and the color gamut of the far-red Q₁ and cyan Q₂primary colors viewed through the second filter F₂. The color gamut of afirst image is depicted in FIG. 6 b by the triangle 632 connecting thered P₁, green P₂ and blue P₃ primary colors. The color gamut of a secondimage is depicted in FIG. 6 b by the line segment 634 connecting thefar-red Q₁ and cyan Q₂ primary colors. The color gamut of the anaglyphmay be a full-color gamut comprising the six hues red, yellow, green,cyan, blue, and magenta. The green hues of the second image may berendered as either nearly white or cyan. This may produce blueish-greenor desaturated green hues in the color gamut of the anaglyph. Red huesof the second image may be rendered as far-red. This may produce redhues in the color gamut of the anaglyph. Blue hues of the second imagemay be rendered as either cyan or nearly white. This may producegreenish-blue or blue hues in the color gamut of the anaglyph. Yellowand magenta hues of the second image may be rendered as nearly white orred hues producing yellow and magenta hues in the color gamut of theanaglyph. Cyan hues may be rendered as cyan hues producing cyan hues inthe color gamut of the anaglyph.

FIG. 7 a depicts the spectra of five primary colors red P₁, green P₂,blue P₃, orange Q₁, and green Q₂ of a five color (OG/RGB) anaglyphhaving a spectral order (P₁, Q₁, Q₂, P₂, P₃). FIG. 7 a also depicts thespectra 722 of a first viewing filter F₁ and a second viewing filter F₂for viewing a OG/RGB anaglyph. The first filter F₁ substantiallytransmits the red P₁, green P₂, and blue P₃ primary colors and blocksthe orange Q₁ and green Q₂ primary colors. The second filter F₂substantially transmits the orange Q₁ and green Q₂ primary colors andblocks the red P₁, green P₂, and blue P₃ primary colors. FIG. 7 bdepicts the red P₁, green P₂, blue P₃, orange Q₁, and green Q₂ primarycolors in a CIE xy chromaticity diagram. The color gamut of a OG/RGBanaglyph displayed with these primary colors and viewed through filtersF₁ and F₂ may be substantially a weighted average of the color gamut ofthe red P₁, green P₂, and blue P₃ primary colors viewed through thefirst filter F₁ and the color gamut of the orange Q₁ and green Q₂primary colors viewed through the second filter F₂. The color gamut of afirst image is depicted in FIG. 7 b by the triangle 732 connecting thered P₁, green P₂ and blue P₃ primary colors. The color gamut of a secondimage is depicted in FIG. 7 b by the line segment 734 connecting theorange Q₁ and green Q₂ primary colors. The color gamut of the anaglyphmay be a full-color gamut comprising the six hues red, yellow, green,cyan, blue, and magenta. The green hues of the second image may berendered as green. This may produce green hues in the color gamut of theanaglyph. Red hues of the second image may be rendered as orange. Thismay produce red hues in the color gamut of the anaglyph. Blue hues ofthe second image may be rendered as yellow. The yellow hues of thesecond image may appear desaturated due to the shift of the white pointtoward yellow when viewing through the filter F₂. These hues may produceblueish-gray or blue hues in the color gamut of the anaglyph. Yellowhues of the second image may be rendered as yellow hues producing yellowhues in the color gamut of the anaglyph. Cyan hues may be rendered asgreen hues producing greenish-cyan hues in the color gamut of theanaglyph. Magenta hues may be rendered as orange or nearly white huesproducing reddish-magenta or desaturated magenta hues in the color gamutof the anaglyph.

An advantage of five-color anaglyphs over six-color anaglyphs is thatthe viewing filters may be less expensive and that comparable displayapparatus may provide brighter five-color anaglyphs than six-coloranaglyphs. The viewing filters for four-color anaglyphs may be even lessexpensive than the viewing filters for five-color anaglyphs. Additionalfour-color anaglyphs of the present invention are discussed below.

Another embodiment of the present invention provides methods to displayanaglyphs using two primary colors {P₁, P₂} to display the first imageand two primary colors {Q₁, Q₂} to display the second image. Thespectral order of the primary colors may include (P₁, Q₁, P₂, Q₂) and(P₁, Q₁, Q₂, P₂) and (P₁, P₂, Q₁, Q₂). These anaglyphs may comprise acolor gamut which is a weighted average of the color gamut of theprimary colors {P₁, P₂} of the first image viewed through the firstviewing filter F₁ and the color gamut of the primary colors {Q₁, Q₂} ofthe second image viewed through the second viewing filter F₂. The colorgamut of the first image may be a reduced color gamut including up tothree color hues in the set {red, yellow, green, cyan, blue, andmagenta}. The color gamut of the second image may be a reduced colorgamut including up to three color hues in the set {red, yellow, green,cyan, blue, and magenta}. The color gamut of the anaglyph may includethe hues which may be included in either color gamuts of the first andsecond images. However the hues which may be included in the colorgamuts of only one of the first and second images may appear in thecolor gamut of the anaglyph at reduced saturation or with a shift inperceived hue. The colors of the each image may be rendered in hueswhich most closely correspond to the hue in the other image or renderedas a desaturated hue.

FIG. 8 a depicts the spectra of four primary colors red P₁, green P₂,yellow Q₁, and blue Q₂ of a four-color (YB/RG) anaglyph having aspectral order (P₁, Q₁, P₂, Q₂). FIG. 8 a also depicts the spectra 822of the first viewing filter F₁ and a second viewing filter F₂ forviewing a YB/RG anaglyph. The first filter F₁ substantially transmitsthe red P₁, and green P₂ primary colors and blocks the yellow Q₁ andblue Q₂ primary colors. The second filter F₂ substantially transmits theyellow Q₁ and blue Q₂ primary colors and blocks the red P₁, and green P₂primary colors. FIG. 8 b depicts the red P₁, green P₂, yellow Q₁, andblue Q₂ primary colors in a CIE xy chromaticity diagram. The color gamutof a YB/RG anaglyph displayed with these primary colors and viewedthrough filters F₁ and F₂ may be substantially a weighted average of thecolor gamut of the red P₁, and green P₂ primary colors viewed throughthe first filter F₁ and the color gamut of the yellow Q₁ and blue Q₂primary colors viewed through the second filter F₂. The color gamut of afirst image is depicted in FIG. 8 b by the line segment 832 connectingthe red P₁, and green P₂ primary colors. The color gamut of a secondimage is depicted in FIG. 8 b by the line segment 834 connecting theyellow Q₁ and blue Q₂ primary colors. The color gamut of the anaglyphmay be a full color gamut comprising the six hues red, yellow, green,cyan, blue, and magenta. The green hues of the second image may berendered as either yellow, yellowish green, nearly white or blue. Thismay produce yellowish-green or desaturated green hues in the color gamutof the anaglyph. Red hues of the second image may be rendered as eitheryellow or unsaturated yellow or nearly white. This may producereddish-orange or desaturated green hues in the color gamut of theanaglyph. Blue hues of the first image may be rendered as either yellowor nearly white. This may produce blue hues in the color gamut of theanaglyph. Yellow and cyan hues of the first image may be rendered asyellow hues producing yellow and cyan hues in the color gamut of theanaglyph. Magenta hues may be rendered as red of nearly white hues forthe first image and blue or nearly white hues for the second imageproducing desaturated magenta hues in the color gamut of the anaglyph.

FIG. 9 a depicts the spectra of four primary colors red P₁, green P₂,green Q₁, and blue Q₂ of a four-color (GB/RG) anaglyph having a spectralorder (P₁, P₂, Q₁, Q₂). FIG. 9 a also depicts the spectra 922 of thefirst viewing filter F₁ and a second viewing filter F₂ for viewing aGB/RG anaglyph. The first filter F₁ substantially transmits the red P₁,and green P₂ primary colors and blocks the green Q₁ and blue Q₂ primarycolors. The second filter F₂ substantially transmits the green Q₁ andblue Q₂ primary colors and blocks the red P₁, and green P₂ primarycolors. FIG. 9 b depicts the red P₁, green P₂, green Q₁, and blue Q₂primary colors in a CIE xy chromaticity diagram. The color gamut of aGB/RG anaglyph displayed with these primary colors and viewed throughfilters F₁ and F₂ may be substantially a weighted average of the colorgamut of the red P₁, and green P₂ primary colors viewed through thefirst filter F₁ and the color gamut of the green Q₁ and blue Q₂ primarycolors viewed through the second filter F₂. The color gamut of a firstimage is depicted in FIG. 9 b by the line segment 932 connecting the redP₁, and green P₂ primary colors. The color gamut of a second image isdepicted in FIG. 9 b by the line segment 934 connecting the green Q₁ andblue Q₂ primary colors. These primary colors may provide anaglyphs withcolor gamuts which lack the hues yellow and cyan. However, the viewingfilters have spectra which may be relatively simple and inexpensive.

Three-color anaglyphs may be compatible with conventional displayapparatus which provide three primary color including red, green, andblue. Red/cyan anaglyphs are the common three-color anaglyphs. Red/cyananaglyphs of the present invention with balanced brightness contrast mayprovide yellowish-green, green and blue hues in the anaglyph. On theother hand, blue/yellow anaglyphs of the present invention with balancedbrightness contrast may provide green, yellowish and red hues. Thesehues of a blue/yellow anaglyph may be considered more important for manypurposes such as displaying people. Therefore, blue/yellow anaglyphsmight be expected to be preferred over red/cyan anaglyphs. However, ablue primary color usually contains little brightness weight whichprovides little dynamic range to carry the brightness contrast of animage. Therefore, blue/yellow anaglyphs of the prior art may not be verysatisfactory.

Another embodiment of the present invention provides methods to displayanaglyphs using two primary colors red P₁ and green P₂ to display thefirst image and one primary color cyan Q₁ to display the second image.These primary colors may provide red, yellowish, and green hues whilealso providing enough dynamic range of brightness in primary color Q₁ tobalance the brightness contrast of the second image. In order to provideenough dynamic range, the Q₁ primary color may have a y chromaticitycoordinate greater than about 0.3 or an effective wavelength longerabout 490 nm in a CIE xy chromaticity diagram.

FIG. 10 a depicts the spectra of three primary colors red P₁, green P₂,and cyan Q₁, of a three-color (C/RG) anaglyph. FIG. 10 a also depictsthe spectra 1022 of the first viewing filter F₁ and a second viewingfilter F₂ for viewing a C/RG anaglyph. The first filter F₁ substantiallytransmits the red P₁, and green P₂ primary colors and blocks the cyan Q₁primary color. The second filter F₂ substantially transmits the cyan Q₁primary color and blocks the red P₁, and green P₂ primary colors. FIG.10 b depicts the red P₁, green P₂, and cyan Q₁ primary colors in a CIExy chromaticity diagram. The color gamut of a C/RG anaglyph displayedwith these primary colors and viewed through filters F₁ and F₂ may besubstantially the col or gamut of the red P₁, and green P₂ primarycolors viewed through the first filter F₁. The color gamut of a firstimage is depicted in FIG. 10 b by the line segment 1032 connecting thered P₁, and green P₂ primary colors. FIG. 10 b depicts the white pointW_(p)′ viewed through the first filter F₁ shifted toward yellow comparedwith a conventional white point W_(p). These primary colors may provideanaglyphs with color gamuts with red, yellowish and green hues, may havenegligible retinal rivalry, and may be viewed with viewing filters whichmay be relatively inexpensive.

White Primary Colors

The anaglyphs of the present invention rendered in primary colors {P₁, .. . , P_(m), Q₁} may have a color gamut which is substantially identicalto the color gamut of the first image viewed using the first filter F₁.However, the white or nearly white colors may appear tinted with the hueof the primary color Q₁ in the stereo view of the anaglyph. In order toreduce the tint of the white colors, the primary color Q₁ may be adesaturated primary color. Herein a desaturated primary color is aprimary color with two or more spectral components which generate a huewhich may be white or nearly white. By using a desaturated primary colorQ₁ for the second image, the white subject matter may appear white toboth eyes and appear white in the stereo view. Herein, a desaturatedprimary color is sometimes called a white primary color without loss ofgenerality.

A desaturated primary color Q₁ may cause a small desaturation of theperceived color in a stereo view of an anaglyph. The amount ofdesaturation depends on the relative luminance of the first and secondimages. As the luminance of the second image decreases, the amount ofdesaturation of the perceived colors may decrease. The desaturation ofthe perceived hues may be compensated for by increasing the saturationof the first image.

Another embodiment of the present invention provides methods to displaythe second image of a stereo pair using a white primary color Q₁. Thewhite primary color Q₁ of the present invention may have a spectrumwhich does not substantially overlap the spectra of the primary colors{P₁, . . . , P_(m)} of the first image. The polarization state p₂ of thewhite primary color Q₁ may be orthogonal of the polarization state p₁ ofthe primary colors {P₁, . . . , P_(m)}. The present embodiment providesseveral methods of providing a white primary color Q₁ with a spectrawhich does not substantially overlap the spectra of the red, green andblue primary colors {P₁, P₂, P₃} of a display apparatus. A white primarycolor may be created by merging two primary colors or two spectralregions into a single primary color. The primary colors {Q₁, Q₂} may bemerged into a single primary color Q by a relationship between primarycolors Q₁ and Q₂. For example,Q ₂=σ₁ Q ₁where σ₁ is a constant. The spectra S_(Q) of the primary color Q may begiven by the relationshipS _(Q)=ω₁ S _(Q1)+φ₂ S _(Q2)where ω₁ and ω₂ are constants and S_(Q1) is the spectra of the primarycolor Q₁ and S_(Q2) is the spectra of the primary color Q₂. The primarycolor Q may be considered a single white primary color Q₁ or acombination of primary colors {Q₁, Q₂}. Herein the primary color Q issometimes considered to be a single primary color Q₁ in order tosimplify the discussion without loss of generality. In general, adesaturated primary color Q may be created from a set of primary colors{Q₁, . . . , Q_(n)} with a set of relationships Q_(j)=σ_(j)Q₁ where theσ_(j) are constants. In general, the spectra S_(Q) of desaturatedprimary color Q may include two or more spectral components {Q₁, . . . ,Q_(n)} with spectra respectively where S_(Q)=ΣωjS_(j) where the ω_(j)are constants.

A first method of creating a white primary color Q is to combine afar-red spectra of light and a cyan spectra of light. If the primarycolor P₁ is red, the primary color P₂ is green, and the primary color P₃is blue; the spectra of the primary color P₁ may substantially notoverlap the spectra of the far-red component of primary color Q and thespectra of the primary colors P₂ and P₃ may substantially not overlapthe spectra of the cyan component of Q. The spectrum of cyan light maybe chosen to produce a near white or yellowish-white primary color Qwhen combined with the red spectral component of Q. For example, cyanlight with a spectrum centered around about 495 nm may be combined withfar-red light with wavelengths longer than about 630 nm to produce anearly white primary color Q₁.

FIG. 6 a depicts the spectra of representative red Q₁ and cyan Q₂components which may be combined to produce a white primary color Q.FIG. 6 a also depicts spectra of viewing filters F₁ and F₂ which may beused to view the anaglyphs produce by this method. FIG. 6 b depicts theprimary colors P₁, P₂, P₃, Q₁, and Q₂ in a CIE chromaticity diagram. Theprimary colors Q which may be produced from primary colors Q₁ and Q₂ isdepicted by the line segment 634 connecting the primary colors Q₁ andQ₂.

A second method of creating a white primary color Q is to combine ayellow or near-red spectra of light and a blue spectra of light. If theprimary color P₁ is red, the primary color P₂ is green, and the primarycolor P₃ is blue; the spectra of the primary colors P₁ and P₂ maysubstantially not overlap the spectra of the yellow component of Q andthe spectra of the primary colors P₂ and P₃ may substantially notoverlap the spectra of the blue component of Q. The spectrum of bluewavelengths may be chosen to produce a near white or yellowish-whiteprimary color Q when combined with the red spectral component of Q. Forexample, blue light with a spectrum centered around about 480 nm may becombined with yellow light with a spectrum centered around 580 nm toproduce a nearly white primary color Q.

FIG. 5 a depicts representative yellow Q₁ and blue Q₂ components whichmay be combined to produce a white primary color Q. FIG. 5 b alsodepicts spectra of viewing filters F₁ and F₂ which may be used to viewthe anaglyphs produce by this method. FIG. 5 b depicts the primarycolors P₁, P₂, P₃, Q₁, and Q₂ in a CIE chromaticity diagram. The primarycolors Q which may be produced from primary colors Q₁ and Q₂ is depictedby the line segment 534 connecting the primary colors Q₁ and Q₂.

A third method of creating a white primary color Q is to combine red R₂,green G₂, and blue B₂ components of light where the red P₁, green P₂,and blue P₃ primary colors may substantially not overlap the spectra ofthe components R₂, G₂, and B₂ of the primary color Q.

FIG. 3 a depicts representative red R₂, green G₂, and blue B₂ componentswhich may be combined to produce the primary color Q. FIG. 3 b alsodepicts spectra of viewing filters F₁ and F₂ which may be used to viewthe anaglyphs produce by this method.

A fourth method of creating a white primary color Q is to combineyellow, cyan and magenta components of light where the spectra of thered P₁, green P₂ and blue P₃ primary colors may substantially notoverlap the spectra of the yellow, cyan and magenta components of Q.

In creating a white primary color Q from a particular light source, itmay be convenient to use the light which is not typically used in theprimary colors used for displaying non-stereoscopic images. In the caseof a metal halide lamp light source, it may be convenient to combine theextra yellow light in the lamp spectrum with cyan or blue light in themetal halide lamp spectrum to produce a white or nearly white primarycolor Q₁. In the case of a xenon lamp light source, it may be convenientto combine the extra red light in the xenon lamp spectrum with cyanlight in the xenon lamp spectrum to produce a white or nearly whiteprimary color Q₁. In the case of LED light sources, it may be convenientto combine red or orange light with cyan light to produce a white ornearly white primary color Q₁ or to combine yellow light with cyan lightto produce a white or nearly white primary color Q₁.

A desaturated primary color {Q} of the present invention may be used ina four-color anaglyph with red, green, blue, and Q primary colors toprovide full-color stereoscopic views. A desaturated primary color {Q}of the present invention may also be used with three-color anaglyphs toimprove the white colors in the stereoscopic view. In one embodiment, ared P₁, and green P₂ primary color may be used to render the first imagewhile a desaturated primary color Q may be used to render the secondimage. The primary color Q may be desaturated from blue by moving theprimary color Q toward cyan. This will desaturate the primary color dueto the lowing tinting strength of cyan hues compared to blue hues. Cyanalso provides more brightness to carry the brightness contrast asdiscussed previously. The primary color Q may be desaturated further byadding far-red wavelengths of the light above about 640 nm or by addingyellow wavelengths near about 580 nm. The viewing filters for a red,green/cyan, far-red anaglyph may be providing by dye filters, ordichroic filters.

Viewing filters may have overlapping transmission spectra in the regionswhere the primary colors have small intensity. For example, a blueprimary color usually contains little brightness weight which provideslittle dynamic range to carry the brightness contrast of an image.

Viewing filters can consist of a first viewing filter F₁ withtransmission spectrum T₁ and a second viewing filter F₂ withtransmission spectrum T₂. In order to selectively view the first imageof the stereoscopic image through the first filter, T₁ should pass largeportions of the luminance of each of the {P₁, . . . , P_(m)} primarycolors and pass at most a small fraction of the luminance of the {Q₁, .. . , Q_(n)} primary colors. In other words, the spectra of each P_(i)should largely overlap T₁ while the spectra of each should not overlapT₁ more than some maximum amount. The maximum levels of transmission ofthe Q_(j) primary colors through the first filter depends on therelative luminance of the Q_(j) primary color compared with theluminance of the {P₁, . . . , P_(m)} primary colors and on the dynamicrange of the display device. Since the Q_(j) primary colors can havemuch lower luminance than the {P₁, . . . , P_(m)} primary colors, the T₁can have a relatively large transmission in the regions of the lowluminance Q_(j) and still satisfy the requirements of the presentinvention. In general, the second image should not be perceived brightlyenough through the first filter to interfere with stereoscopicperception.

In order to selectively view the second image of the stereoscopic imagethrough the second filter, T₂ should pass large portions of theluminance of each of the {Q₁, . . . , Q_(n)} primary colors and pass atmost a small fraction of the luminance of the {P₁, . . . , P_(m)}primary colors. In other words, the spectra of each should largelyoverlap T₂ while the spectra of each P_(i) should not overlap T₁ morethan some maximum amount. The maximum levels of transmission of theP_(i) primary colors through the second filter depends on the relativeluminance of the P_(i) primary color compared with the luminance of the{Q₁, . . . , Q_(n)} primary colors and on the dynamic range of thedisplay device.

Display of Generalized Anaglyphs

Some embodiments of the present invention provide methods of processingstereoscopic images which may be different than the methods ofprocessing non-stereoscopic images.

Another embodiment of the present invention provides a mode (2D mode)for displaying non-stereoscopic images and a mode (3D mode) fordisplaying stereoscopic images comprising a display apparatus providingt primary colors {T₁, . . . , T_(t)}. In a 2D mode of the displayapparatus, the primary colors {T₁, . . . , T_(t)} may be used to displaya non-stereoscopic images. A transformation G₅ may be used to transformthe coordinates {A₁, . . . , A_(r)} of a non-stereoscopic image into theprimary colors {T₁, . . . , T_(t)} where the number r of coordinates maybe different from the number t of primary colors. In a 3D mode of thedisplay apparatus, the primary colors {T₁, . . . , T_(t)} may be used todisplay a stereoscopic images as anaglyphs. A transformation G₁ may beused to transform the coordinates {A₁, . . . , A_(r)} of a first imageinto the primary color coordinates {P₁, . . . , P_(m)} and atransformation G₂ may be used to transform the coordinates {B₁, . . . ,B_(s)} of a second image into the primary color coordinates {Q₁, . . . ,Q.}. Then the coordinates {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)}may be transformed into the display primary colors {T₁, . . . , T_(t)}by a transformation G₄ where the set of primary colors {T₁, . . . ,T_(t)} may be the union of the set of primary colors {P₁, . . . , P_(m)}and the set of primary colors {Q₁, . . . , Q_(n)}. The sets of primarycolors {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} may be selectable bythe user. The transformations G₁ and G₂ may be selected to balance thebrightness contrast of like subject matter of the first and secondimages of stereoscopic pairs. The display apparatus may be switched fromthe 2D display mode to 3D display modes either as a result of thedisplay apparatus detecting stereoscopic content or as a result of anaction of the user.

The 2D display mode and 3D display mode of the display apparatus may besummarized as follows:

In general, the transformation G₄ used for stereoscopic images may bedifferent from the transformation G₅ used for displayingnon-stereoscopic images. For example, a display apparatus may includered T₁, green T₂, blue T₃ and white T₄ primary colors. If the displayapparatus receives a single image in red A₁, green A₂ and blue A₃coordinates, the display apparatus may use the transformation G₅ totransform the three image coordinates {A₁, A₂, A₃} into four displayprimary colors {T₁, T₂, T₃, T₄}. The transformation G₅ may distributepart of the brightness of the image into the white primary color T₄ andpart of the brightness of the image into the primary colors {T₁, T₂,T₃}. Examples of transformations G₅ are provided in the prior art andare well known to those skilled in the art. If the display apparatusreceives or generates an anaglyph in four coordinates {P₁, P₂, P₃, Q₁},the display apparatus may use the transformation G₄ to transform thecoordinate Q₁ into the white primary color T₄ and transform thecoordinates {P₁, P₂, P₃} into the primary colors {T₁, T₂, T₃}. Thetransformation G₄ may compensate for various properties of the displayapparatus such as the properties of the primary colors {T₁, . . . ,T_(t)} and color shifts in an anaglyph due to fusing two images withdifferent color gamuts.

The anaglyphs of the present invention may be created either outside adisplay apparatus or created by a display apparatus. If the anaglyphsare created by the display apparatus using transformations G₁ and G₂,the display apparatus may (1) receive the stereoscopic image coordinatesthrough a connection or connections to a storage apparatus; (2) convertthe stereoscopic image coordinates to anaglyph primary colorcoordinates, and (3) load the anaglyph coordinates into the primarycolors of the display apparatus using the transformation G₄. If theanaglyphs are created outside the display apparatus, the displayapparatus may (1) receive the anaglyph primary color coordinates througha connection or connections to a storage apparatus; (2) load theanaglyph coordinates into the primary colors of the display apparatususing the transformation G₄. The display apparatus and storage apparatusmay be components of a composite apparatus such as a digital televisionapparatus which may include additional methods to receive and decompressstereoscopic content transmitted in certain formats.

Another embodiment of the present invention comprises a switch SW₁ bywhich a user may switch a display apparatus between a 2D display modeand the 3D display mode of the present invention. The switch SW₁ mayalso provide a method for a user to adjust the average brightness of thesecond image relative to the average brightness of the first image. Theswitch SW₁ may allow a display apparatus to be switched between aplurality of states. One state of the display apparatus may correspondto the 2D mode of the display apparatus while a plurality of states maycorrespond to the 3D mode of the display apparatus with a plurality ofbrightness levels of the second image. Then the switch SW₁ may provide asimple intuitive method for a user to adjust the display apparatus for2D and 3D content and a means to adjust the ratio of the averagebrightness of the second image to the average brightness of the firstimage to the preferred average brightness level of the second image. Alow average brightness level of the second image may facilitate viewinganaglyph content simultaneously in 2D without using viewing filters andin 3D using viewing filters by multiple users. The switch SW₁ may becomposed of hardware or may be provided in software or firmware or acombination thereof.

Transfer of Generalized Anaglyphs

In the prior art, a display apparatus which is capable of displayingstereoscopic images often display first and second images timesequentially. This often reduces the display frequency or refresh rateof the display apparatus by a factor of two. If the display apparatus isalso capable of displaying non-stereoscopic images with a refresh ratef₂, the display apparatus often may display a stereoscopic images with arefresh rate of f₁=f₂/2 which is half the refresh rate fornon-stereoscopic display.

The methods of displaying stereoscopic images as two full color imagesof the prior art may be summarized as follows:{A ₁ , . . . ,A _(r) }→{W ₁ , . . . ,W _(w) }→{T ₁ , . . . ,T _(t)} atfrequency f ₂/2 and{B ₁ , . . . ,B _(s) }→{W ₁ , . . . ,W _(w) }→{T ₁ , . . . ,T _(t)} atfrequency f ₂/2where W is a buffer with w channels {W₁, . . . , W_(w)} for storing thecolor coordinates of the display primary colors {T₁, . . . , T_(t)}before the primary colors are updated. Herein a buffer has enoughchannels to store the coordinates stored in them unless otherwisestated.

Methods of displaying traditional anaglyphs often differ from methods ofdisplaying stereoscopic images composed of two full color images in thatanaglyphs may often be treated like a single image by a displayapparatus whereas stereoscopic full-color image pairs may be treated astwo images during display. If the refresh rate of a display apparatusfor displaying non-stereoscopic images is f₂, the refresh rate fordisplaying anaglyphs images may also be f₂.

The methods of displaying anaglyphs of the prior art may be summarizedas follows:{P ₁ ,P ₂ ,Q ₁ }→{W ₁ , . . . ,W _(w) }→{T ₁ , . . . ,T _(t)} atfrequency f ₂where W is a buffer with w channels {W₁, . . . , W_(w)} for storing thecolor coordinates of the display primary colors {T₁, . . . , T_(t)}before the primary colors are updated.

The present invention provides methods for displaying general anaglyphsat a refresh rate f₃ equal to the refresh rate f₂ of displayingnon-stereoscopic images f₃=f₂. However, the methods of the presentinvention may receive the first and second images at the combinedfrequency f₄ which may be twice the frequency of the displayingnon-stereoscopic images f₄=2f₂. In contrast, traditional stereoscopicdisplays which display two full-color images receive the first andsecond images at a frequency f₄ equal to the frequency of displayingnon-stereoscopic images f₄=f₂. For this reason, display apparatus of thepresent invention may receive images at twice the frequency ofconventional display apparatus. The display apparatus of the presentinvention may comprise hardware, firmware and software to process thestereoscopic images which may be received at twice the frequency oftraditional display apparatus.

Another embodiment of the present invention provides a method fordisplaying stereoscopic images comprising a display apparatus providingprimary colors {T₁, . . . , T_(t)} which may be refreshed at a rate f₂.The display apparatus may receive a first image in coordinates {A₁, . .. , A_(r)} at a frequency of f₂, and receive a second image in colorcoordinates {31, . . . , B_(s)} at the frequency f₂ where the combinedfrequency f₄ of receiving first and second images is given by f₄=2f₂.The display apparatus may include a transformation G₁ which transformsthe coordinates {A₁, . . . , A_(r)} into the primary coordinates {P₁, .. . , P_(m)} and a transformation G₂ which transforms the coordinates{B₁, . . . , B_(s)} into the primary coordinates {Q₁, . . . , Q_(n)}.The coordinates {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} may bestored in a buffer W with w channels {W₁, . . . , W_(w)} where w isequal to or greater than t. The display apparatus may transform thedisplay coordinates {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} intophysical primary colors {T₁, . . . , T_(t)} at the frequency f₂. Inother words, the display apparatus of the present invention may receiveimages at a rate f₄ which is twice the refresh rate f₂ of the primarycolors {T₁, . . . , T_(t)}.

The method of the present embodiment may be summarized as follows:

Another embodiment of the present invention provides methods to transferstereoscopic images to a display apparatus for displaying as anaglyphs.The first image coordinates {A₁, . . . , A_(r)} may be received by thedisplay apparatus through a first communication port C with e channels{C₁, . . . , C_(e)} at a frequency f₂. Herein a communication port hasenough channels to carry the coordinates transferred unless otherwisestated. The second image coordinates {B₁, . . . , B_(s)} may be receivedby the display apparatus through a second communication D with echannels {D₁, . . . , D_(e)} at frequency f₂. The combined frequency ofreceiving first and second images may be f₄=2f₂. The first imagecoordinates received by the display apparatus may be stored in a firstmemory buffer {U} with b channels {U₁, . . . , U_(b)}. The second imagecoordinates received by the display apparatus may be stored in a secondmemory buffer {V} with c channels {V₁, . . . , V_(c)}. The coordinatesin buffers U and V may be transformed into anaglyph primary coordinates{P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} using transformations G₁ andG₂ respectively. The coordinates {P₁, . . . , P_(m)} and {Q₁, . . . ,Q_(n)} may be stored in a buffer {W} with w channels {W₁, . . . , W_(w)}where w is equal to or greater than t. Then the coordinates {P₁, . . . ,P_(m)} and {Q₁, . . . , Q_(n)} may be transformed into the primarycolors {T₁, . . . , T_(t)} at a frequency f₂.

FIG. 11 a depicts a method for receiving anaglyph images by a displayapparatus 1102 from an external source 1104 by receiving a first imagein primary coordinates {P} through communication port {C} and byreceiving a second image in primary coordinates {Q} throughcommunication port {D}. The first image may be received into a buffer{U} of the display apparatus. The second image may be received into abuffer {V} of the display apparatus. The display apparatus may include atransformation G₄ which maps the primary coordinates {P} stored inbuffer {U} and primary coordinates {Q} stored in buffer {V} into theprimary colors {T} of the display apparatus. The external source mayinclude a transformation G₁ for transforming a first image in colorcoordinates {A} into primary coordinates {P}. The external source mayinclude a transformation G₂ for transforming a second image in colorcoordinates {B} into color coordinates {Q}.

FIG. 11 b depicts a method for receiving stereoscopic images by adisplay apparatus 1106 from an external source 1108 by receiving a firstimage in color coordinates {A} through communication port {C} and byreceiving a second image in color coordinates {B} through communicationport {D}. The first image may be received into a buffer {U} of thedisplay apparatus. The second image may be received into a buffer {V} ofthe display apparatus. The display apparatus may include atransformation G₁ for transforming the first image in color coordinates{A} stored in buffer {U} into primary coordinates {P}. The displayapparatus may include a transformation G₂ for transforming a secondimage in color coordinates {B} stored in buffer {V} into primarycoordinates {Q}. The display apparatus may include a transformation G₄which maps the primary coordinates {P} and primary coordinates {Q} intothe primary colors {T} of the display apparatus.

Another embodiment of the present invention provides methods to transferstereoscopic images to a display apparatus time sequentially for displayas anaglyphs. The first image coordinates {A₁, . . . , A_(r)} may bereceived by the display apparatus through a first communication port {C}with e channels {C₁, . . . , C_(e)} in a first interval of time t₁. Thesecond image coordinates {B₁, . . . , B_(s)} may be received by thedisplay apparatus through communication port {C} in a second interval oftime t₂. The first image coordinates received by the display apparatusmay be stored in a first memory buffer {U} with b coordinates {U₁, . . ., U_(b)}. The second image coordinates received by the display apparatusmay be stored in a second memory buffer {V} with c coordinates {V₁, . .. , V_(c)}. The coordinates in buffers {U} and {V} may be transformedinto anaglyph primary coordinates {P₁, . . . , P_(m)} and {Q₁, . . . ,Q_(n)} using transformations G₁ and G₂ respectively. The coordinates{P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} may be stored in a buffer Wwith w channels {W₁, . . . , W_(w)} where w is equal to or greater thant. Then the coordinates {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} maybe transferred into the display primary colors {T₁, . . . , T_(t)} in athird interval of time t₃

Either the first or second image may be transferred to the displayapparatus first. The transformations G₁ and G₂ may be applied in timeintervals which overlap the time intervals t₁ or t₂. For example if thesecond image is transferred to the buffer {V} first, the coordinates{B₁, . . . , B_(s)} may be transformed into the coordinates {Q₁, . . . ,Q_(n)} using transformation G₂ before or during the transfer of thecoordinates {A₁, . . . , A_(r)} to the buffer {U}.

FIG. 12 a-c depicts a method for transferring stereoscopic images timesequentially to the display apparatus. The display apparatus 1202 may beconnected to a storage apparatus 1204 by a communication port {C}. Theinitial full-color stereoscopic image or an anaglyph image may bereceived by the display apparatus through the connector {C}. FIG. 12 adepicts the first image in coordinates {A} being transferred to thebuffer {U} of the display apparatus from the storage apparatus during afirst duration of time t₁. FIG. 12 b depicts the second image incoordinates {B} being transferred to the buffer {V} of the displayapparatus during a second duration of time t₂. FIG. 12 c depicts theanaglyph coordinates {P} and {Q} being transformed into the displayprimary colors {T₁, . . . , T_(s)} in a third duration of time t₃. Thedisplay apparatus may include a transformation G₁ for transforming thecolor coordinates {A} in the buffer {U} into the primary coordinates{P}. The display apparatus may include a transformation G₂ fortransforming the color coordinates {B} in the buffer {V} into theprimary coordinates {Q}.

Another embodiment of the present invention provides methods to transferstereoscopic images to a display apparatus time sequentially for displayas anaglyphs. The display apparatus may provide primary colors {T₁, . .. , T_(t)}. The first image coordinates {A₁, . . . , A_(r)} may betransferred to the display apparatus through a first communication portC with e channels {C₁, . . . , C_(e)} in a first interval of time t₁.The first image coordinates received by the display apparatus may bestored in a memory buffer {U} with b coordinates {U₁, . . . , U_(b)}.The coordinates of the first image stored in buffer {U} may betransformed into anaglyph primary coordinates {P₁, . . . , P_(m)} usinga transformation G₁. The coordinates {P₁, . . . , P_(m)} may be storedin a buffer W with w channels {W₁, . . . , W_(w)} where w is equal to orgreater than t. The second image coordinates {B₁, . . . , B_(s)} may betransferred to the display apparatus through communication port C in asecond interval of time t₂. The second image coordinates received by thedisplay apparatus may be stored in the memory buffer U. The coordinatesof the second image in buffer {U} may be transformed into anaglyphcoordinates {Q₁, . . . , Q_(n)} using the transformation G₂. Thecoordinates {Q₁, . . . , Q_(n)} may be stored in the buffer W. Thecoordinates {P₁, . . . , P_(m)} and {Q₁, . . . , Q_(n)} may betransferred from the buffer W into the display primary colors {T₁, . . ., T_(t)} in a third interval of time t₃:

Either the first or second images may be transferred to the displayapparatus first. The transformation G₁ may be applied in a time intervalwhich overlaps the time interval t₂. The transformation G₂ may beapplied in time interval which overlaps the time interval t₁. Forexample if the second image is transferred to the buffer {V} first, thedisplay apparatus may transform the coordinates {B₁, . . . , B_(s)} intothe coordinates {Q₁, . . . , Q_(n)} using the transformation G₂ beforeor during the transfer of the coordinates {A₁, . . . , A_(r)} to thebuffer {U}. Then the coordinates in buffer {U} may be transformed intothe coordinates {P₁, . . . , P_(m)} using the transformation G₁.

FIG. 13 a-c depicts a method for transferring stereoscopic image datatime sequentially to the display apparatus. The display apparatus 1302may be connected to a storage apparatus 1304 by a communication port{C}. The initial full-color stereoscopic image or an anaglyph image maybe received by the display apparatus through the connector {C}. FIG. 13a depicts the first image in coordinates {A} being transferred to thebuffer {U} of the display apparatus from the storage apparatus during afirst duration of time t₁. FIG. 13 a depicts the coordinates of thefirst image {A} being transformed into the anaglyphs coordinates {P}using a transformation G₁ during the time interval t₁. FIG. 12 b depictsthe second image in coordinates {B} being transferred to the buffer {V}of the display apparatus during a second duration of time t₂. FIG. 12 bdepicts the coordinates of the second image {B} being transformed intothe anaglyphs coordinates {Q} using a transformation G₂ during timeinterval t₂. FIG. 12 c depicts the anaglyph coordinates {P} and {Q}being transformed into the display primary colors {T₁, . . . , T_(s)} ina third duration of time t₃.

Compressing Four-Color Anaglyphs into Three Channels

In some cases it may be desirable to transfer anaglyph images to adisplay apparatus through a single communication port at the frequency fof updating the primary colors of a display apparatus. If thecommunication port C has channels e channels {C₁, . . . , C_(e)} and theanaglyph has e=m+n primary color coordinates {P₁, . . . , P_(m)} {Q₁, .. . , Q_(n)}, then the anaglyph may be received by the display apparatusthrough communication port {C} at a frequency f and transformed into theprimary colors {T₁, . . . , T_(t)} of the display apparatus at frequencyf. However, if the number e of channels in the communication port {C} isless than the number m+n of anaglyph coordinates, then the anaglyphcoordinates may be compressed into e coordinates {E₁, . . . , E_(e)}using a transformation G₃ of the present invention before being receivedby the display apparatus. The display apparatus may include atransformation G₃ ⁻¹ of the present invention which may transform thecoordinates {E₁, . . . , E_(e)} into the primary coordinates {P₁, . . ., P_(m)} {Q₁, . . . , Q_(n)}.

Another embodiment of the present invention provides methods to compressthe coordinates {P₁, P₂, P₃, Q₁} of a four-color anaglyph into threecoordinates {E₁, E₂, E₃} using a transformation G₃. The three channelsmay be received by a display apparatus through a three channelcommunication port {C}. The display apparatus may comprise atransformation G₃ ⁻¹ for uncompressing the three color channels {E₁, E₂,E₃} into the four color coordinates {P₁, P₂, P₃, Q₁}. FIG. 14 a depictsa display apparatus 1402 receiving from an external source 1404 ananaglyph compressed into coordinates {E} through communication port {C}.The external source may include a transformation G₃ which may be used totransform the anaglyph coordinates {P} and {Q} into coordinates {E}. Thedisplay apparatus may include a transformation G₃ ⁻¹ which may be usedto transform the coordinates {E} anaglyph into coordinates {P} and {Q}.

The transformation G₃ may transform the anaglyph coordinates 1P₁, . . ., P_(m) of the first image into the coordinates {E₁, E₂} and transformthe anaglyph coordinate {Q₁} into the coordinate {E₃}. FIG. 14 b depictsthe transformation G₃ transforming coordinates {P₁, P₂, P₃} into thecoordinates {E₁, E₂} and transforming the coordinate {Q₁} intocoordinate {E₃}.

Another embodiment of the present invention provides a method tocompress the coordinates {P₁, P₂, P₃} into the coordinates {E₁, E₂}. Thecoordinates {E₁} may contain the brightness Y₁ of the first image whilethe coordinates {E₂} may contain compressed chromaticity coordinates C₁and C₂ of the first image. The two chromaticity coordinates may be C₁=xand C₂=y where x and y are the chromaticity coordinates of the CIE xyYcolor space. Alternatively, the two chromaticity coordinates may beC₁=R-G and C₂=B-G. Then during decompression, G may be determined fromthe constraint that the brightness Y₁ which may be represented in thecoordinates {E₁} may be a function of the red R, green G, and blue Bcolor coordinates.

The chromaticity coordinates C₁ and C₂ may be compressed in one channelby encoding the color at reduced spatial resolution. If the verticalresolution is reduced by a factor of two, the coordinate images {C₁} and{C₂} may be arranged in the coordinate image {E₂} one over the other. Ifthe horizontal resolution is reduced by a factor of two, the coordinateimages {C₁} and {C₂} may be arranged in the coordinate image {E₂} onebeside the other. The display apparatus may provide a transformation G₃⁻¹ which transforms the chromaticity images in one channel into fullresolution chromaticity images. FIG. 15 b depicts the brightnesscoordinates Y₁ of the first image in the channel E₁ and the chromaticitycoordinates C₁ and C₂ with reduced vertical resolution in the channel E₂placed one over the other. Alternately the chromaticity coordinates maybe interlaced in the E₂ channel.

Another embodiment of the present invention provides methods to transferthe color information of the first image in one channel at halfresolution in both the vertical and horizontal directions. This allowsfor four reduced resolution versions of the image to be packed into onechannel. For example, reduced resolution red, green and blue images maybe transferred in channel E₂ while the brightness of the same image maybe transferred at full resolution in channel E₁. The display apparatusmay provide a transformation G₃ ⁻¹ which transforms the reducedresolution color images to full resolution. The brightness Y_(c) of theup-scaled images may be computed and compared with the brightness valuesY₁ in the channel E₁. Then the color images may be modified to reducethe error between the calculated Y_(c) and transferred Y₁ brightnessvalues. FIG. 15 b depicts the brightness Y₁ of the first image inchannel E₁ and the reduced resolution color images Small Red, SmallGreen, and Small Blue in channel E₂. FIG. 15 b also depicts an extra(Extra) quadrant of the channel E₂. The extra channel may containadditional information such as a fourth primary color coordinates orinformation helpful in decompressing the image color.

The compression formats of the present invention may be relativelysimple in order that a display apparatus may decompress the formats withsubroutines that may be similar to subroutines that the displayapparatus may to use for displaying non-stereoscopic images.

Three-channel format {E₁, E₂, E₃} of a stereo image of the presentinvention may be convenient for distribution and storage of full-colorstereoscopic images. Many image compression methods exist in the priorart for three or more channel data such as JPEG, PNG, MPEG and manyothers. These compression methods may be used with the three channelformat of the present invention to conveniently storage and distributestereo images.

As noted above, the present invention is applicable to primary colors,color transformations and special filters and is believed to beparticularly useful for displaying and viewing anaglyphs with wide colorgamuts without retinal rivalry. The present invention should not beconsidered limited to the particular examples described above, butrather should be understood to cover all aspects of the invention asfairly set out in the attached claims. Various modifications, equivalentprocesses, as well as numerous structures to which the present inventionmay be applicable will be readily apparent to those of skill in the artto which the present invention is directed upon review of the presentspecification. The claims are intended to cover such modifications anddevices.

Display Types

In order to display and view the general anaglyphs of the presentinvention, it is beneficial for the spectra of the primary colors {P₁, .. . , P_(m)} of the first image to not substantially overlap the primarycolors {Q₁, . . . , Q_(n)} of the second image or for the polarizationstate p₁ of the primary colors {P₁, . . . , P_(m)} to be orthogonal tothe polarization state p₂ of the primary colors {Q₁, . . . , Q_(n)}.Then a first F₁ viewing filter and a second F₂ viewing filter may beused to view the stereoscopic images. The first viewing filter F₁ maysubstantially transmit the primary colors {P₁, . . . , P_(m)} and blockthe primary colors {Q₁, . . . , Q_(n)}. The second viewing filter F₂ maysubstantially transmit the primary colors {Q₁, . . . , Q_(n)} and blockthe primary colors {P₁, . . . , P_(m)}. If the spectra of the primarycolors do not substantially overlap, the viewing filters may be colorfilters. If the polarization states of the primary colors are opposite,the viewing filters may be polarized filters. Alternatively, the firstand second images may be displayed time sequentially and viewed withshutter filters which may alternate between transparent and opaquestates in synchronization with the first and second images. Anotherembodiment of the present invention the first and second images may bedisplayed on separate surfaces (a case of spatial multiplexing) and aviewing apparatus used to direct the view of each image to first andsecond eyes of a user respectively. Autostereoscopic display methods area case of spatial multiplexing which may be used to view anaglyphs ofthe present invention.

The present invention discloses methods to provide four or more primarycolors in various display types in order to display the generalanaglyphs of the present invention. Providing four primary colors may begenerally easier and cheaper than providing six primary colors requiredin the prior art to display two full color stereoscopic image pairs.Methods of providing six primary colors usually may be adapted toprovide four to six primary colors of the present invention.

Display apparatus which may provide four or more primary colors fordisplaying anaglyphs of the present invention may include: digitalprojectors such as DLP, LCD and LCOS projectors, front and rearprojectors; analog projectors; CRT's; flat panel LCD displays; plasmadisplays; flat panel LED displays; printers; autostereoscopic displaysor prints; Lippman photographic records and other types.

In some embodiments of the present invention, the primary colors may bespatially multiplexed as in multi-colored pixel array displays that useseparate regions of each pixel to generate each primary color. Pixeldisplay apparatus may be either direct view such as flat panel displaysor indirect view such as digital projectors. In some embodiments of thepresent invention, at least some of the primary colors may be timemultiplexed in order to time multiplex the left and right images of astereo pair. Time multiplexing display apparatus may be either directview such as flat panel LED displays and plasma displays, or indirectview such as digital projectors utilizing a color wheel or alternatinglight sources. In some embodiments of the present invention, at leastsome of the primary colors may be layer multiplexed. Layer multiplexingdisplay apparatus may be either direct view such as printed images,multilayer LCD displays or photographic slide film or indirect view suchas multilayer LCD projectors and photographic slide film projectors.Some embodiments of the present invention provide four or more primarycolor images by forming primary images in multiple light paths withmultiple panel display devices. The primary images may be combined usingdichroic prisms or polarization beam splitters PBS. Display apparatuswith multiple light paths may be direct view such as dual flat panelstereoscopic displays or indirect view such as digital projectors, andslide projectors. Some embodiments of the present invention may useseveral types of multiplexing which may include spatial multiplexing,time multiplexing, layer multiplexing, and multiple light paths in adisplay apparatus to generate four or more primary colors for displayinganaglyphs of the present invention.

A direct view display apparatus of the present invention which displaysthe first and second images in orthogonal polarization states may beviewed with polarized viewing filters to obtain a stereoscopic view ofthe stereoscopic images. An indirect view display apparatus of thepresent invention which displays the first and second images inorthogonal polarization states may project the image onto a polarizationpreserving screen and viewed with polarized viewing filters to obtain astereoscopic view of the stereoscopic images. In direct view displayapparatus of the present invention, providing polarization encoding ofthe first and second images a polarization preserving screen may not benecessary.

Herein some examples of embodiments of the present invention whichprovide four primary colors for displaying the anaglyphs of the presentinvention are described.

Four-Color Projectors

Another embodiment of the present invention provides a method ofdisplaying stereoscopic images comprising four primary colors {P₁, P₂,P₃, Q} and four display panels. A bundle of generally white light{L_(w)} may be separated into four light bundles {L₁, L₂, L₃, L₄}comprising the spectra of primary colors {P₁, P₂, P₃, Q} respectivelyusing optical components such as dichroic filters and PBS; or fourbundles of light {L₁, L₂, L₃, L₄} may be formed using multiple lightsources. The light bundles {L₁, L₂, L₃, L₄} may be incident on displaypanels {DP₁, DP₂, DP₃, D₄} respectively. Display panel {DP₁, DP₂, DP₃,D₄} may impart a primary coordinates {P₁, P₂, P₃, Q} to light bundles{L₁, L₃, L₃, L₄} respectively. The light bundles {L₁, L₂, L₃, L₄} may becombined using optical components such as dichroic filters and PBS'sinto a projectable light bundle {L_(P)} Then the bundle {L_(P)} may beprojected through a projection lens. The display panels {DP₁, DP₂, DP₃}may impart the color coordinates {P₁, P₂, P₃} of a first image intolight bundles {L₁, L₃, L₃} respectively. The display panel {DP₄} mayimpart the coordinates {Q} of a second image into light bundle {L₄}. P₁may be a red primary color. P₂ may be a green primary color. P₃ may be ablue primary color. Q may be a red, yellow, green, cyan, blue, ordesaturated primary color comprising components {Q₁, . . . Q_(n)}. A setof polarization filters, polarization rotators, or color selectivepolarization filters CSPF may be used to set the polarization state p₂of the primary color {Q} orthogonal to the polarization state p₁ of theprimary colors {P₁, P₂, P₃}. If the polarization states of primarycolors {P₁, P₂, P₃} are orthogonal to the polarization state of primarycolor {Q}, the spectra of the primary color {Q} may overlap the spectraof the primary colors {P₁, P₂, P₃}. Then the primary color {Q} maypreferably be red, orange, yellow, cyan or white. Color filters such asdichroic filters, CSPF's and dye filters may be used to control thespectra of the primary colors so that the spectra of the primary colors{P₁, P₂, P₃} may substantially not overlap the spectra of the primarycolor {Q}. Then the primary color {Q} may preferably be far-red, yellow,cyan, or white.

In another embodiment of the present invention utilizes a first cube PBSand second cube PBS to direct four light bundles {L₁₁, L₁₂, L₁₃, L₁₄}onto four LCOS display panels—one bundle onto each panel. The first cubePBS has a first and a second LCOS display panel positioned parallel tosecond and third sides of the first cube PBS respectively. The secondcube PBS has a third and fourth LCOS display panel positioned parallelto second and third sides of the second cube PBS respectively. The firstPBS separates light entering a first side into first and second primarycolor light bundles and directs the light bundles onto first and secondLCOS panels. The first and second LCOS panels impart first and secondprimary color images to the first and second light bundles respectivelyand reflect the first and second light bundles toward the first PBS. Thefirst PBS combines the first and second light bundles and directs themout of a fourth side of the first PBS. The second PBS separates lightentering a first side into first and second primary color light bundlesand directs the light bundles onto third and fourth LCOS panels. Thethird and fourth LCOS panels impart third and fourth primary colorimages to the first and second light bundles respectively and reflectthe third and fourth light bundles toward the second PBS. The second PBScombines the third and fourth light bundles and directs them out of afourth side of the second PBS.

FIG. 16 depicts an optical assembly 1600 which may be part of a displayapparatus of the present invention comprises four liquid crystal onSilicon (LCOS) display panels and four polarization beam splitters(PBS). The configuration is similar to the QuadColor™ architecture fromColorlink. There are many variations of this general architecture whichwill be obvious to those skilled in the art. The optimal pairing ofprimary colors may depend on the choice of the wavelengths of theprimary color {Q}. In FIG. 16, polarized light 1640 comprising thespectra of the primary colors {P₁, P₂, P₃, Q} passes through a CSPF1620. CSPF 1620 switches the polarization state of the spectra of twoprimary colors {P₂, Q}. The spectra of the primary colors {P₁, P₂, P₃,Q} enters a first PBS 1602. PBS 1602 divides the primary colors into twolight bundles. The spectra of primary colors {P₂, Q} pass through thefirst PBS 1602 and pass through a second CSPF 1626. CSPF 1626 switchesthe polarization state of the spectra of the primary color {Q}. Thespectra of primary colors {P₂, Q} enters a second PBS 1608 whichseparates the primary colors into a first and second light bundlescomprising primary colors {P₂, Q} respectively. The spectra of primarycolor {Q} passes through the PBS 1608 and may be incident on a firstLCOS panel 1616 and may be reflected back toward PBS 1608. The firstpanel 1616 imparts a primary image to the spectra of primary color {Q}.The spectra of primary color {P₂} may be reflected by PBS 1608 and maybe incident on a second LCOS panel 1618 and may be reflected back towardPBS 1608. The second panel 1618 imparts a primary image to the spectraof primary color {P₂}. The second PBS 1608 combines the light bundles ofthe primary colors {P₂, Q} and directs them out of PBS 1608.

The spectra of primary colors {P₁, P₃} may be reflected by the first PBS1602 and pass through a third CSPF 1622. CSPF 1622 switches thepolarization state of the spectra of the primary color {P₃}. The spectraof primary colors {P₁, P₃} enters a third PBS 1604 which separates theprimary colors into a third and fourth light bundles comprising primarycolors {P₁, P₃} respectively. The spectra of primary color {P₃} passesthrough the PBS 1604 and may be incident on a third LCOS panel 1614 andmay be reflected back toward PBS 1604. The third panel 1614 imparts aprimary image to the spectra of primary color {P₃}. The spectra ofprimary color {P₁} may be reflected by PBS 1604 and may be incident on afourth LCOS panel 1612 and may be reflected back toward PBS 1604. Thesecond panel 1612 imparts a primary image to the spectra of primarycolor {P₁}. The third PBS 1604 combines the light bundles of the primarycolors {P₁, P₃} and directs them out of PBS 1604.

The spectra of primary colors {P₂, Q} passes through a fourth CSPF 1628.The CSPF 1628 switches the polarization state of the spectra of primarycolor {Q}. The spectra of primary colors {P₂, Q} may be reflected by afourth PBS 1606. The spectra of primary colors {P₁, P₃} passes through afifth CSPF 1624. The CSPF 1624 switches the polarization state of thespectra of primary color {P₃}. The spectra of primary colors {P₁, P₃}pass through a fourth PBS 1606. PBS 1606 combines the spectra of theprimary colors {P₂, Q} and the spectra of the primary colors {P₁, P₃}.The spectra of primary colors {P₁, P₂, P₃, Q} pass through a projectionlens 1602. The spectra of the primary colors {P₁, P₂, P₃, Q} may passthrough a fifth CSPF 1630. CSPF 1630 may switch the polarization stateof the primary colors {P₁, P₂} or {P₂, Q} to obtain one polarizationstate p₁ for all primary colors {P₁, P₂, P₃, Q}. Or CSPF 1630 may switchthe polarization state of the primary color {P₂} to obtain a firstpolarization state p₁ for all primary colors {P₁, P₂, P₃} and a secondpolarization state p₂ for primary color {Q}. The present embodiment mayinclude additional optical components that condition the spectra of theprimary colors and the paths of the primary colors.

Another embodiment of the present invention provides a method ofdisplaying stereoscopic images comprising four primary colors {P₁, P₂,P₃, Q} and three display panels. A bundle of generally white light{L_(W)} may be separated into four light bundles {L₁, L₂, L₃, L₄}comprising the spectra of primary colors {P₁, P₂, P₃, Q} respectivelyusing optical components such as dichroic filters, PBS, and colorwheels; or four bundles of light {L₁, L₂, L₃, L₄} may be formed usingmultiple light sources such as LED lamps. A color wheel may generally beused to create time sequential bundles of light. The light bundles {L₁,L₂, L₃} may be incident on a display panels {DP₁, DP₂, DP₃}. The lightbundle {L₄} may be incident on a display panel Display panels {DP₁, DP₂,DP₃} may impart primary coordinates {P₁, P₂, P₃, Q} to light bundles{L₁, L₃, L₃, L₄}. The light bundles {L₁, L₂, L₃, L₄} may be combinedusing optical components such as dichroic filters and PBS's into aprojectable light bundle {L_(P)}. Then the light bundle {L_(P)} may beprojected through a projection lens. The display panel {DP₁} may impartthe primary color coordinates {P₁} to the light bundle {L₁}. The displaypanel {DP₂} may impart the primary color coordinates {P₂} to the lightbundle {L₂}. The display panel {DP₃} may impart the primary colorcoordinates {P₃} to the light bundle {L₃}. At least one display panel{DP_(j)} from the set of display panels {DP₁, DP₂, DP₃} may impartprimary color coordinates {Q} to the light bundle {L₄}. The lightbundles {L_(j),L₄} may be time sequentially incident on the displaypanel {DP_(j)}. The display panel {DP_(j)} may time sequentially impartthe coordinates {P_(j)} to the light bundle {L_(j)} and impart thecoordinates {Q} to the light bundle {L₄}. P₁ may be a red primary color.P₂ may be a green primary color. P₃ may be a blue primary color. Q maybe a red, yellow, green, cyan, blue, or desaturated primary colorcomprising components {Q₁, . . . Q_(n)}. A set of polarization filters,polarization rotators, or CSPF may be used to set the polarization statep₂ of the primary color {Q} orthogonal to the polarization state p₁ ofthe primary colors {P₁, P₂, P₃}. If the polarization states of primarycolors {P₁, P₂, P₃} are orthogonal to the polarization state of primarycolor {Q}, the spectra of the primary color {Q} may overlap the spectraof the primary colors {P₁, P₂, P₃}. Then the primary color {Q} maypreferably be red, orange, yellow, cyan or white. Color filters such asdichroic filters, CSPF's and dye filters may be used to control thespectra of the primary colors so that the spectra of the primary colors{P₁, P₂, P₃} may substantially not overlap the spectra of the primarycolor {Q}. Then the primary color {Q} may preferably be far-red, yellow,cyan, or white.

In another embodiment of the present invention, the primary color {Q}may comprise more than one spectral component {Q₁, Q₂}, then the lightbundle {L₄} may comprise two light bundles {L_(q1),L_(q2)}. The lightbundles {L_(q1),L_(q2)} may be time sequentially incident on two displaypanels {DP_(j), DP_(k)} with light bundles {L_(j),L_(k)} respectively.The display panels {DP_(j), PD_(k)} may time sequentially impart thecoordinates {Q₁, Q₂} to the light bundles {Lq₁, L_(q2)}.

Another embodiment of the present invention comprises a dichroic X-cubeand three display panels {DP₁, DP₂, DP₃}. The dichroic X-cube may acceptlight bundles on three sides and reflect them using an ‘X’ configurationof dichroic prisms as a combined light bundle {L_(P)} through a fourthside. The display panels may be LCOS, LCD, or digital micro mirrordisplays DMD. Light bundles {L₁, L₂, L₃} comprising the spectra ofprimary colors {P₁, P₂, P₃} may be incident of the display panels {DP₁,DP₂, PD₃} respectively. Light bundle {L_(q1)} comprising the spectra ofa component {Q₁} of primary color {Q} may be incident on display panel{DP_(j)}. The light bundles {L_(j),L_(q1)} may be combinedtime-sequentially by a dichroic mirror or dichroic prism. Light bundle{L_(q2)} comprising the spectra of a component {Q₂} of primary color {Q}may be incident on display panel {DP_(k)}. The light bundles{L_(k),L_(q2)} may be combined time-sequentially by a dichroic mirror ordichroic prism. The display panel {DP₁} may impart coordinates {P₁} ofthe first image to the light bundle {L₁}. The display panel {DP₂} mayimpart coordinates {P₂} of the first image to the light bundle {L₂}. Thedisplay panel {DP₃} may impart coordinates {P₃} of the first image tothe light bundle {L₃}. The display panel {DP_(j)} may time sequentiallyimpart coordinates {Q} of the second image to the light bundle {L_(j)}time and impart coordinates {P_(j)} of the first image to the lightbundle {L_(j)}. The display panel {DP_(k)} may time sequentially impartcoordinates {Q} of the second image to the light bundle {L_(q2)} andimpart coordinates {P_(k)} of the first image to the light bundle{L_(k)}.

FIG. 17 depicts an optical assembly 1700 which may be part of a displayapparatus of the present invention comprising three LCOS display panels,three PBS's, a dichroic X-cube, and a dichroic beamsplitter. There aremany variations of this general architecture which will be obvious tothose skilled in the art. In FIG. 17, light bundles {L₁, L₂, L₃, L_(q1)}comprising the spectra of four primary colors {P₁, P₂, P₃, Q₁} enter theassembly at four locations. The spectra of the primary color {P₁} entersa first dichroic prism 1742 and may be reflected toward a first PBS1702. The first PBS 1702 reflects a polarized spectra of primary color{P₁} toward a first LCOS display panel 1712. The first display panel1712 imparts primary coordinates {P₁} to the spectra of primary color{P₁} and reflects the spectra of primary color {P₁} back into the firstPBS 1702. The spectra of primary color {P₁} passes through the first PBS1702 and enters a dichroic X-cube 1746. The spectra of primary color{P₁} may be reflected by dichroic X-cube 1746 toward the projection lens1702. The spectra of the primary color {Q₁} enters the first dichroicprism 1742 and may be reflected toward the first PBS 1702. The first PBS1702 reflects a polarized spectra of primary color {Q₁} toward the firstLCOS display panel 1712. The first display panel 1712 imparts primarycoordinates {Q} to the spectra of primary color {Q₁} and reflects thespectra of primary color {Q₁} back into the first PBS 1702. The spectraof primary color {Q₁} passes through the first PBS 1702 and enters thedichroic X-cube 1746. The spectra of primary color {Q₁} may be reflectedby dichroic X-cube 1746 toward the projection lens 1702. The spectra ofthe primary color {P₂} enters a second PBS 1704. The second PBS 1704reflects a polarized spectra of primary color {P₂} toward a second LCOSdisplay panel 1714. The second display panel 1714 imparts primarycoordinates {P₂} to the spectra of primary color {P₂} and reflects thespectra of primary color {P₂} back into the second PBS 1704. The spectraof primary color {P₂} passes through the second PBS 1704 and enters thedichroic X-cube 1746. The spectra of primary color {P₂} passes throughdichroic X-cube 1746 toward the projection lens 1702. The spectra of theprimary color {P₃} enters a third PBS 1706. The third PBS 1706 reflectsa polarized spectra of primary color {P₃} toward a third LCOS displaypanel 1716. The third display panel 1716 imparts primary coordinates{P₃} to the spectra of primary color {P₃} and reflects the spectra ofprimary color {P₃} back into the third PBS 1706. The spectra of primarycolor {P₃} passes through the third PBS 1706 and enters the dichroicX-cube 1746. The spectra of primary color {P₃} may be reflected bydichroic X-cube 1746 toward the projection lens 1702. The projectionlens projects the spectra of the primary colors {P₁, P₂, P₃, Q₁}. Thesource of the light bundles comprising the spectra often primary colors{P₁, P₂, P₃, Q₁} may be a single lamp for which the spectra of theprimary colors may be separated by additional optical components such asdichroic filters, PBS and color wheels. Or the source may comprisemultiple lamps such as red, green, and blue LED's and a Q₁ LED. Thelight comprising spectra of the primary color {P₁} and light comprisingthe primary color {Q₁} enter dichroic prism 1742 time sequentially. Thefirst display panel 1712 imparts the coordinates {P₁, Q₁} to the spectraof primary colors {P₁, Q₁} time sequentially. Optionally, a CSPF 1730may set the polarization state p₂ of the primary color {Q₁} orthogonalto the polarization state p₁ of the primary colors {P₁, P₂, P₃}. Thepresent embodiment may include additional optical components thatcondition the primary color spectra and paths. In another embodiment,the third display panel may time sequentially impart the coordinates {Q}to a spectra of a primary color {Q₂}. The spectra of primary colors {P₃}and {Q₂} may enter a second dichroic prism 1744. The spectra of theprimary color {Q₂} may be reflected by the second dichroic prism 1744toward the third PBS 1706. The spectra of the primary color {P₃} maypass through the second dichroic prism 1744 toward the third PBS 1706.The spectra of primary colors {Q₁, Q₂} may form a single desaturatedprimary color {Q}.

Another embodiment of the present invention provides a method ofdisplaying stereoscopic images comprising four primary colors {P₁, P₂,P₃, Q} and two display panels. A bundle of generally white light {L_(W)}may be separated into four light bundles {L₁, L₂, L₃, L₄} comprising thespectra of primary colors {P₁, P₂, P₃, Q} respectively using opticalcomponents such as dichroic filters, PBS, and color wheels; or fourbundles of light {L₁, L₂, L₃, L₄} may be formed using multiple lightsources such as LED lamps. A color wheel may generally be used to createtime sequential bundles of light. The light bundles {L₁,L₄} may be timesequentially incident on a display panels {DP₁}. The light bundles{L₂,L₃} may be time sequentially incident on a display panels {DP₂}.Display panels {DP₁, DP₂} may impart primary coordinates {P₁, P₂, P₃, Q}to light bundles {L₁, L₃, L₃, L₄}. The light bundles {L₁, L₂, L₃, L₄}may be combined using optical components such as dichroic filters andPBS's into a projectable light bundle {L_(P)}. Then the light bundle{L_(P)} may be projected through a projection lens. The display panel{DP₁} may impart the primary color coordinates {P₁} to the light bundle{L₁} time sequentially. The display panel {DP₁} may impart the primarycolor coordinates {Q} to the light bundle {L₄} time sequentially. Thedisplay panel {DP₂} may impart the primary color coordinates {P₂} to thelight bundle {L₂} time sequentially. The display panel {DP₂} may impartthe primary color coordinates {P₃} to the light bundle {L₃} timesequentially. P₁ may be a red primary color. P₂ may be a green primarycolor. P₃ may be a blue primary color. Q may be a red, yellow, green,cyan, blue, or desaturated primary color comprising components {Q₁, . .. Q_(n)}. A set of polarization filters, polarization rotators, or CSPFmay be used to set the polarization state p₂ of the primary color {Q}orthogonal to the polarization state p₁ of the primary colors {P₁, P₂,P₃}. If the polarization states of primary colors {P₁, P₂, P₃} areorthogonal to the polarization state of primary color {Q}, the spectraof the primary color {Q} may overlap the spectra of the primary colors{P₁, P₂, P₃}. Then the primary color {Q} may preferably be red, orange,yellow, cyan or white. Color filters such as dichroic filters, CSPF'sand dye filters may be used to control the spectra of the primary colorsso that the spectra of the primary colors {P₁, P₂, P₃} may substantiallynot overlap the spectra of the primary color {Q}. Then the primary color{Q} may preferably be far-red, yellow, cyan, or white.

Another embodiment of the present invention provides a method ofdisplaying stereoscopic images comprising four primary colors {P₁, P₂,P₃, Q} and a display panel. A bundle of generally white light {L_(W)}may be separated into four light bundles {L₁, L₂, L₃, L₄} comprising thespectra of primary colors {P₁, P₂, P₃, Q} respectively using opticalcomponents such as dichroic filters, PBS, and color wheels; or fourbundles of light {L₁, L₂, L₃, L₄} may be formed using multiple lightsources such as LED lamps. A color wheel may generally be used to createtime sequential bundles of light. The light bundles {L₁, L₂, L₃, L₄} maybe time sequentially incident on a display panels {DP₁}. Display panel{DP₁} may impart primary coordinates {P₁, P₂, P₃, Q} to light bundles{L₁, L₃, L₃, L₄}. The light bundles {L₁, L₂, L₃, L₄} may be combinedusing optical components such as dichroic filters and PBS's into aprojectable light bundle {L_(P)}. Then the light bundle {L_(P)} may beprojected through a projection lens. The display panel {DP₁} may impartthe primary color coordinates {P₁} to the light bundle {L₁} timesequentially. The display panel {DP₁} may impart the primary colorcoordinates {P₂} to the light bundle {L₂} time sequentially. The displaypanel {DP₁} may impart the primary color coordinates {P₃} to the lightbundle {L₃} time sequentially. The display panel {DP₁} may impart theprimary color coordinates {Q} to the light bundle {L₄} timesequentially. P₁ may be a red primary color. P₂ may be a green primarycolor. P₃ may be a blue primary color. Q may be a red, yellow, green,cyan, blue, or desaturated primary color comprising components {Q₁, . .. Q_(n)}. A set of polarization filters, polarization rotators, or CSPFmay be used to set the polarization state p₂ of the primary color {Q}orthogonal to the polarization state p₁ of the primary colors {P₁, P₂,P₃}. If the polarization states of primary colors {P₁, P₂, P₃} areorthogonal to the polarization state of primary color {Q}, the spectraof the primary color {Q} may overlap the spectra of the primary colors{P₁, P₂, P₃}. Then the primary color {Q} may preferably be red, orange,yellow, cyan or white. Color filters such as dichroic filters, CSPF'sand dye filters may be used to control the spectra of the primary colorsso that the spectra of the primary colors {P₁, P₂, P₃} may substantiallynot overlap the spectra of the primary color {Q}. Then the primary color{Q} may preferably be far-red, yellow, cyan, or white. The display panelmay be a LCD, digital micro mirror device DMD, or LCOS display panel orother display panel.

FIG. 18 a depicts an optical assembly 1800 which may be part of adisplay apparatus of the present invention comprising a LCD displaypanel 1814, a light source not shown, a color wheel 1850, and aprojection lens 1802. The light source may provide a generally whitelight L_(w) comprising the spectra of the primary colors {P₁, P₂, P₃,Q}. The light L_(w) passes through the color wheel 1850 and may beincident on the display panel 1814. The color wheel 1850 alternatelypasses the primary colors {P₁, P₂, P₃, Q} in synchronization with thedisplay panel 1814 imparting primary coordinates {P₁, P₂, P₃, Q} to theprimary colors {P₁, P₂, P₃, Q}. The primary colors {P₁, P₂, P₃, Q} maybe projected time sequentially through the projection lens. Optionally,a CSPF 1830 may set the polarization state p₂ of the primary color Qorthogonal to the polarization state p₁ of the primary colors {P₁, P₂,P₃}. The present embodiment may include additional optical componentsthat condition the primary color spectra and paths. FIG. 18 b depictsthe color wheel 1850. The color wheel alternately positions filterswhich pass primary colors {P₁, P₂, P₃, Q₁} it the path of a light L_(w).

FIG. 19 depicts an optical assembly 1900 which may be part of a displayapparatus of the present invention comprising a DMD display panel 1914.In this embodiment, light may be reflected by the display panel 1814through the projection lens 1930. The light incident on the displaypanel 1814 comprises time sequential spectra of the primary colors {P₁,P₂, P₃, Q}. The primary colors may be alternated time sequentially usinga color wheel 1950. Optionally, polarization filter and a CSPF 1930 mayset the polarization state p₂ of the primary color Q orthogonal to thepolarization state p₁ of the primary colors {P₁, P₂, P₃}. The presentembodiment may include additional optical components that condition theprimary color spectra and paths.

FIG. 20 depicts an optical assembly which may be part of a displayapparatus of the present invention comprising a light source and amulticolor panel display such as a four-color LCD display panel 2014.The LCD display panel 2014 may form light bundles {L₁, L₂, L₃, L₄}comprising the spectra of the primary colors {P₁, P₂, P₃, Q}respectively in a spatially multiplexed pixel pattern as shown in FIGS.21 and 22. A spatially patterned color filter may pass the primarycolors {P₁, P₂, P₃, Q} through specific regions of the LCD display panel2014 creating the pixel pattern of light bundles {L₁, L₂, L₃, L₄}. Thedisplay panel 2014 may modulate the light bundles {L₁, L₂, L₃, L₄}imparting the primary color coordinates {P₁, P₂, P₃, Q} to the lightbundles {L₁, L₂, L₃, L₄} respectively. Herein light bundles {L_(X)}comprising the spectra of primary color X_(j) is sometimes called theprimary color {X_(j)}. The primary coordinates {Xj} may refer to thenumerical values representing the level of primary color {Xj}. Generallywhite light L_(W) 2064 comprising the spectra of the primary colors {P₁,P₂, P₃, Q} may be incident on the display panel 2014. Spatiallymultiplexed primary colors 2062 modulated by the display panel 2014 forma projectable bundle of light L_(P) 2062. The light L_(P) 2062 may beprojected by the projection lens 2002. Optionally, a CSPF 2030 may setthe polarization state p₂ of the primary color Q orthogonal to thepolarization state p₁ of the primary colors {P₁, P₂, P₃}. The presentembodiment may include additional optical components that condition theprimary color spectra and paths.

Four Color Flat Panel Displays

Direct view display devices may comprise display panels with spatiallymultiplexed primary colors where the primary colors are separated intoregions of a surface called pixels. The surface is populated with atwo-dimensional array of pixels whose primary color elements may bemodulated to display a color image. Traditional display panels providethree primary colors red, green and blue. Some display panels providered, green. blue, and white primary colors where the white primary colorgenerally may comprise the spectra of the red, green and blue primarycolors. Herein direct view displays are sometimes called flat paneldisplays although some direct view displays may be CRT's and rearprojection displays. Direct view displays may include liquid crystaldisplays LCD, plasma display panels PDP, organic electroluminescentdisplay ELD, light emitting diode LED displays, field emission displayFED, and light emitting polymer LEP displays. LCD display panelsgenerally provide polarized primary colors with identical polarizationstates. PDP and LED display panels generally provide non-polarizedprimary colors.

One embodiment of the present invention comprises a flat panel displayproviding an array of pixels with four sub-pixel elements {x₁, x₂, x₃,x₄} having either rectangular areas or square areas. The elements {x₁,x₂, x₃, x₄} may provide primary colors {P₁, P₂, P₃, Q₁} capable ofdisplaying images represented in primary color coordinates {P₁, P₂, P₃,Q₁} where the spectra of the primary color {Q₁} may substantially notoverlap the spectra of the primary colors {P₁, P₂, P₃}. The primarycolors {P₁, P₂, P₃} may be used to display a first image. The primarycolors {Q₁} may be used to display a second image. An LCD display panelof the present invention may comprise a patterned color filter whichdetermine the spectra of the primary colors {P₁, P₂, P₃, Q₁}. A PDPdisplay panel of the present invention may comprise a set of phosphors{s1, s2, s3, s4} which determine the spectra of the primary colors {P₁,P₂, P₃, Q₁}. A LED display panel of the present invention may comprisefour types of LED's emitting four color spectra. The primary color P₁may be red. The primary color P₂ may be green. The primary color P₃ maybe green. The primary color Q₁ may comprise spectral components: far-red(greater than about 640 nm), orange (about 590 nm-615 nm), yellow (about570-590 nm), cyan (about 480-500 nm), or blue (about 460-480 nm)components. The primary color {Q₁} may comprise one or more spectralcomponents.

FIG. 21 depicts a first pixel pattern 2100 providing four primary colors{P₁, P₂, P₃, Q₁} in four rectangular areas which fit inside a squarepixel. FIG. 22 depicts a second pixel pattern 2200 providing fourprimary colors {P₁, P₂, P₃, Q₁} in four square areas which fit inside asquare pixel. These pixel patterns may be manufactured by well known tothose skilled in the art.

One embodiment of the present invention comprises a flat panel displayproviding an array of pixels with four sub-pixel elements {x₁, x₂, x₃,x₄} having either rectangular areas or square areas. The elements {x₁,x₂, x₃, x₄} may provide primary colors {P₁, P₂, P₃, Q₁} capable ofdisplaying images represented in primary color coordinates {P₁, P₂, P₃,Q₁} where the polarization state p₂ of the primary color {Q₁} may beorthogonal to the polarization state of the primary colors {P₁, P₂, P₃}.The spectra of the primary color {Q₁} may overlap the spectra of theprimary colors {P₁, P₂, P₃}. The primary colors {P₁, P₂, P₃} may be usedto display a first image. The primary colors {Q₁} may be used to displaya second image. An LCD, PDP, or LED display panel of the presentinvention may comprise a patterned polarization rotator layer whichswitches the polarization state of the primary color {Q₁} to state p₂.An LCD, PDP, or LED display panel of the present invention may comprisea CSPF layer which switches the polarization state of the primary color{Q₁} to p₂. An LCD, PDP or LED display panel of the present inventionmay comprise a polarized filter to polarize the primary colors {P₁, P₂,P₃, Q₁}.

FIG. 24 depicts a LCD display panel of the present invention. Thedisplay comprises subpixels elements {x₁, x₂, x₃, x₄}. The spectra ofthe primary colors {P₁, P₂, P₃, Q₁} may be determined by a patternedcolor filter not shown. Generally white light L_(W) comprising thespectra of the primary colors {P₁, P₂, P₃, Q₁} enters from the back sideof the display panel and travels through a first polarized filter. Thepolarized light travels through a liquid crystal layer may compriseliquid crystal cells that may rotate the polarized light by selectableamounts. The polarization rotated light is filtered by a secondpolarization filter which modulates the intensity of transmitted lightwith polarization state p₁. The patterned color filter transmits thespectra of the primary colors. A patterned polarization rotator mayswitch the polarization state of the light transmitted through theelement x₄ to the state p₂ whereby the polarization state p₁ of theprimary colors {P₁, P₂, P₃} may be orthogonal to the polarization statep₂ of the primary color {Q₁}. The polarization rotator may comprisebirefringent material forming a ½ wave plate.

FIG. 25 depicts a LCD display panel of the present invention. Thedisplay comprises subpixels elements {x₁, x₂, x₃, x₄}. The specta of theprimary colors {P₁, P₂, P₃, Q₁} may be determined by a patterned colorfilter not shown. Generally white light L_(w) comprising the spectra ofthe primary colors {P₁, P₂, P₃, Q₁} enters from the back side of thedisplay panel and travels through a first polarized filter. Thepolarized light travels through a liquid crystal layer may compriseliquid crystal cells that may rotate the polarized light by selectableamounts. The polarization rotated light is filtered by a secondpolarization filter which modulates the intensity of transmitted lightwith polarization state p₁. The patterned color filter transmits thespectra of the primary colors. A polarization rotator may switch thepolarization state of the light transmitted through the element x₄ tothe state p₂ whereby the polarization state p₁ of the primary colors{P₁, P₂, P₃} may be orthogonal to the polarization state p₂ of theprimary color {Q₁}. The polarization rotator may comprise a CSPF.

Another embodiment of the present invention comprises an LCD displaypanel containing multi-colored pixels and a time multiplexed lightsource. The display panel may comprise an array of pixels with threesub-pixel regions {x₁, x₂, x₃} providing primary colors {P₁, P₂, P₃}respectively while at least one region {x₁} may provide primary color{Q₁} where the spectra of the primary colors {P₁, P₂, P₃} maysubstantially not overlap the spectra of the primary color {Q₁}. Thedisplay panel may have an alternating backlight which allows the region{x_(i)} to provide primary colors {P_(i)} and {Q₁} time sequentially.The backlight may comprise a first light source providing the spectra ofprimary color {P_(i)} and lacking the spectra of primary color {Q₁}; anda second light source providing the spectra of primary color {Q₁} andlacking the spectra of primary color The backlight may be switchedrapidly between the first and second light sources providing the primarycolors {P_(i)} and {Q₁} time sequentially. During a first interval oftime t₁ the first light source may provide the spectra of primary color{Pi} and the region {x_(i)} may be used to display the coordinate{P_(i)} of a first image. During a second interval of time t₂ the secondlight source may provide the spectra of primary color {Q₁} and theregion {x_(i)} may be used to display the coordinate {Q₁} of a secondimage. The remaining coordinates of {P₁, P₂, P₃} of the first image maybe displayed using the remaining regions of {x₁, x₂, x₃} using eitherthe first, second or a third light source.

FIG. 23 depicts an LCD panel with two sources which may be LED lightsources. The primary colors {P₁, P₂, P₃} may be red, green, and bluerespectively. The primary color {Q₁} may be yellow.

Another embodiment of the present comprises an LCD display panelcomprising an array of pixels with three sub-pixel regions {x₁, x₂, x₃}and a backlight with two types of backlighting which may be providedwith two light sources. A first type of backlighting may provide thespectra of primary colors {P₁, P₂, P₃} for displaying non-stereoscopicimages. A second type of backlighting may provide the spectra of primarycolors {P₁, P₂, Q₁} for displaying stereoscopic images. as three-coloranaglyphs. The first type of backlighting may be provided by a firstlight source. The second type of backlighting may be provided by thesecond light source or the first and second light sources. The spectraof the primary color {Q₁} may be preferable for displaying a secondimage of a stereoscopic pair of images while the spectra of the primarycolor {P₃} may be preferable for displaying a full-colornon-stereoscopic image. In one embodiment, the primary color {P₃} may bea blue primary color and the primary color {Q₁} may be a cyan primarycolor.

More Projectors

Another embodiment of the present invention utilizes two conventionalprojectors to display the stereoscopic images as anaglyphs. Externalfilters may be used to modify the primary colors of the projectors sothat a first projector provides primary colors {P₁, P₂, P₃} and a secondprojector provides primary colors {Q₁} where the spectra of the primarycolors {P₁, P₂, P₃} may substantially not overlap the spectra of theprimary color {Q₁}. The first projector may display a first image inprimary colors {P₁, P₂, P₃}. The second projector may display a secondimage in primary color {Q₁}. The first and second images may betransformed into primary color coordinates {P₁, P₂, P₃, Q₁} by anexternal device such as a computer.

FIG. 26 depicts a first projector 2642 and a second projector 2602positioned near to the first projector 2642. A first filter F₁ 2626 ispositioned between a projection lens 2614 of the first projector 2642and a viewing screen 2608. A second filter F₂ 2624 is positioned betweena projection lens 2604 of the second projector 2602 and a viewing screen2608. The first projector may project a first image 2612 through thefilter 2626 in primary colors {P₁, P₂, P₃}. The filter 2626 may removelight comprising the spectra of primary color {Q₁} from the spectra ofthe primary colors {P₁, P₂, P₃}. The second projector may project agrayscale second image 2610 through the filter 2624 in primary colors{P₁, P₂, P₃}. The filter 2624 may transmit light comprising the spectraof primary color {Q₁}. Then the first image may be viewed with a thirdcolor filter F₃ and the second image may be viewed through a fourthcolor filter F₄. The transmission spectra of the third filter F₃ may besimilar to the transmission spectra of the first filter F₁. Thetransmission spectra of the fourth filter F₄ may be similar to thetransmission spectra of the second filter F₂.

Another embodiment of the present invention comprises a projector withan internal filter F₂ which may transmit primary color {Q₁} and blockprimary colors {P₁, P₂, P₃}. The filter F₂ may be movable whereby filterF₂ may be positioned in the projection path or out of the projectionpath. If the filter F₂ is in the projection path, the projector mayproject the primary colors {Q₁}. If the filter F₂ is out of theprojection path, the projector may project the primary colors {P₁, P₂,P₃}. The projector may comprise an internal filter F₁ which may transmitprimary colors {P₁, P₂, P₃} and block primary colors {Q₁}. The filter F₁may be movable whereby filter F₁ may be positioned in the projectionpath or out of the projection path. If the filter F₁ is in theprojection path, the projector may project the primary colors {P₁, P₂,P₃} whose spectra may not substantially overlap the spectra of primarycolor {Q₁}. If the filter F₁ is out of the projection path, theprojector may project the primary colors {P₁, P₂, P₃} whose spectra mayoverlap the spectra of primary color {Q₁}. Two projectors of the presentembodiment may be used to provide primary colors {P₁, P₂, P₃} fordisplaying a first image and primary colors {Q₁} for displaying a secondimage where the spectra of the first and second images may substantiallynot overlap. One projector of the present embodiment may be used todisplay non-stereoscopic images. The first and second images may bedisplayed with balanced brightness contrast for like subject matter.

FIG. 27 depicts a projector 2702 with an adjustable internal filter2730. The filter may be positioned near to the projection lens 2704. Theprojected primary colors 2706 onto viewing screen 2708 may be changed bymoving the adjustable filter 2730. Adjustable filter 2730 may comprise afirst filter F₁ 2732, and a second filter F₂ 2734, and a third filter2736. The third filter may be a transparent media such as air.

Another embodiment of the present invention comprises a projector with amovable filter F₃. In one position, the filter may provide primarycolors {P₁, P_(m)} or {P₁, P_(m+1)} for displaying non-stereoscopicimages. In a second position, the filter may provide primary colors {P¹,. . . , P_(m), Q₁} for displaying stereoscopic images. A first image maybe displayed in primary colors {P₁, . . . , P_(m)} while a second imagemay be displayed in primary color {Q₁}. The first and second images maybe displayed with balanced brightness contrast for like subject matter.

Another embodiment of the present invention comprises a conventionalthree projector and an external optical device which splits theprojected image in half into a first image and a second image. Theexternal optical device modifies the spectra and direction of projectedlight such that the first image may be projected in primary colors {P₁,. . . , P_(m)} and the second image may be projected in primary color{Q₁} where the first and second images may be superimposed on a surface.The first image may be projected on a first half the display outputimage while the second image is projected on a second half of thedisplay output image. The second image brightness coordinate {Y_(Q)} maybe projected in primary colors {T₁, . . . , T_(t)} in the projector. Twoexamples of the optical device are shown in FIGS. 28 a and 29 a.

FIG. 28 b depicts the display output divided into first and secondimages. The first image may be projected on the left side of the displayoutput and the second image may be projected on the right side of thedisplay output. The screen image depicts the first and second imagessuperimposed. The screen image may have a portrait format.

FIG. 28 a depicts a projector 2802 projecting a stereoscopic imagethrough projection lens 2804 and through the optical device. The opticaldevice comprises a first filter 2832, a second filter 2834, a firstmirror 2862, and a second mirror 2864. The first filter 2832 maysubstantially transmit primary colors {P₁, . . . , P_(m)} and blockprimary color {Q₁}. The second filter 2834 may substantially transmitprimary color {Q₁} and block primary colors {P₁, . . . , P_(m)}. Theprojector may project the first and second images onto the first filter2832 and second filter 2834 respectively. The first image may passthrough the first filter 2832 and may be modified by the first filter2832 by removing the spectra of primary color {Q₁}. The first image maythen be reflected by the first mirror 2862 onto a screen 2808. Thesecond image may pass through the second filter 2834 and may be modifiedby the second filter 2834 by removing the spectra of primary colors {P₁,. . . , P_(m)}. The second image may then be reflected by the secondmirror 2864 onto the screen 2808. The first mirror 2862 and secondmirror 2864 may have a slightly different orientations so that the firstand second images may be superimposed by the reflection off the mirrors.

FIG. 29 b depicts the display output divided into first and secondimages. The first image may be projected on the left side of the displayoutput and the second image may be projected on the right side of thedisplay output. The screen image depicts the first and second imagessuperimposed. The screen image may have a landscape format.

FIG. 29 a depicts a projector 2902 projecting a stereoscopic imagethrough projection lens 2904 and through the optical device. The opticaldevice comprises a third mirror 2902, a first filter 2932, a secondfilter 2934, a first mirror 2962, and a second mirror 2964. Theprojector may project the first and second images onto the third mirror2902. The third mirror 2902 may reflect the image by 90 degrees onto thefirst and second filters respectively. The first filter 2932 maysubstantially transmit primary colors {P₁, . . . , P_(m)} and blockprimary color {Q₁}. The second filter 2934 may substantially transmitprimary color {Q₁} and block primary colors {P₁, . . . , P_(m)}. Thefirst image may pass through the first filter 2932 and may be modifiedby the first filter 2932 by removing the spectra of primary color {Q₁}.The first image may then be reflected by the first mirror 2962 onto ascreen 2908. The second image may pass through the second filter 2934and may be modified by the second filter 2934 by removing the spectra ofprimary colors {P₁, . . . , P_(m)}. The second image may then bereflected by the second mirror 2964 onto the screen 2908. The firstmirror 2962 and second mirror 2964 may have a slightly differentorientations so that the first and second images may be superimposed bythe reflection off the mirrors.

FIG. 30 depicts a projector 3002 comprising an objective lens 3004.Light 3006 projected from projector 3002 may form a stereoscopic imageon a screen 3008.

FIG. 31 depicts a projector 3102 comprising a first objective lens 3104and a second objective lens 3114. First light 3110 projected from theprojector 3102 may form part of a stereoscopic image on a screen 3108.Second light 3112 projected from the {acute over (p)}rojector 3102 mayform part of a stereoscopic image on a screen 3108.

Stereoscopic Camera

Stereoscopic camera designs are common in the prior art. Thesestereoscopic cameras often lack a simple inexpensive method to previewthe stereoscopic content comparable to the function of a viewfinder fornon-stereoscopic content. There is a need for a stereoscopic viewfinderwhich may be comparable in size, form, and function to non-stereoscopicviewfinders. Some embodiments of the present invention comprise astereoscopic viewfinder which provides four primary colors fordisplaying stereoscopic images.

Another embodiment of the present invention provides a method tophotographically capture and display stereoscopic content. The methodmay comprise a camera apparatus to photographically capture stereoscopiccontent and a display apparatus to display stereoscopic content. Thecamera apparatus may capture stereoscopic content by any method of theprior art. For example the apparatus may comprise a first objective lensoptically cooperative with a first image sensor and a second objectivelens optically cooperative with a second image sensor. The first andsecond lenses may be positioned apart by the distance of the stereobase. A stereo base is the distance between the first and secondobjective lenses in a stereoscopic camera. The optical axes of the firstand second lenses may be generally directed toward the common subject.The axes may be generally parallel or the axes may intersect at a smallangle at a distance from the lenses in a direction toward the commonsubject. The angle between the axes may be adjustable. The distancebetween the first and second lenses may be adjustable The first andsecond sensor images may be periodically sampled and processed fordisplay on the display apparatus.

The display apparatus may provide four primary colors {P₁, P₂, P₃, Q₁}where the first images from the first sensor may be displayed using theprimary colors {P₁, P₂, P₃} and the second images from the second sensormay be displayed using the primary color {Q₁}. The primary colors {P₁,P₂, P₃} may include red, green, and blue primary colors which allow thefirst images to be displayed in full color. The primary colors {Q₁} maybe a red, yellow, green, cyan, blue or white primary color. The spectraof the primary colors {P₁, P₂, P₃} may substantially not overlap thespectra of the primary color {Q₁}. Then the stereoscopic images may beviewed through first F₁ and second F₂ viewing filters. Alternatively,the polarization state p₁ of the primary colors {P₁, P₂, P₃} may beorthogonal to the polarization state p₂ of the primary color {Q₁}. Thenthe stereoscopic images may be viewed through polarized filters F₁ andF₂. The first filter F₁ may substantially transmit the primary colors{P₁, P₂, P₃} of the first image and block the primary color {Q₁} of thesecond image. The second filter F₂ may substantially transmit theprimary color {Q₁} of the second image and block the primary colors {P₁,P₂, P₃} of the first image. The display apparatus may comprise apolarization filter to polarize the primary colors {P₁, P₂, P₃, Q₁}. Thedisplay apparatus may comprise a CSPF to rotate the polarization stateof the primary color {Q₁} to the state p₂.

This embodiment may include a storage apparatus to storage stereoscopiccontent, a transformation G₁ of the first images into the primary colors{P₁, P₂, P₃}, a transformation G₂ of the second images into the primarycolor {Q₁} whereby the brightness contrast of the first and secondimages may be balanced while displayed in the primary colors {P₁, P₂,P₃, Q₁}. This embodiment may further comprise a second sensor whichprimarily senses the brightness of the second image and a first sensorwhich primarily senses the primary color values of the first image. Thisembodiment may also include a communication port which allows liveimages to be transferred to an external display apparatus.

I claim:
 1. An apparatus for displaying an anaglyph stereoscopic image,the stereoscopic image comprising a first image and a second image, theapparatus configured to: provide m primary colors P₁, . . . , P_(m),wherein m is at least two, and wherein primary color P₁ is green;provide a de-saturated primary color Q₁ comprising: a first spectralcomponent S₁; and a second spectral component S₂, the spectrum of thegreen primary color substantially between the first component S₁ and thesecond component S₂, the combined spectra of first S₁ and second S₂components comprising a de-saturated color; display the first image inprimary colors P₁, . . . , P_(m); and display the second image inde-saturated primary color Q₁.
 2. The apparatus of claim 1, whereinfirst component S₁ is yellow, and second component S₂ is one of blue orcyan.
 3. The apparatus of claim 1, wherein first component S₁ is red,and second component S₂ is cyan.
 4. The method of claim 1, whereinprimary color P₂ is red, and primary color P₃ is blue.
 5. The apparatusof claim 1 further comprising: a first color filter for viewing thefirst image, wherein the first filter transmits luminance L₁ of combinedm primary colors P₁, . . . , P_(m), transmits luminance L₁₁ ofde-saturated primary color Q₁, and luminance L₁ substantially greaterthan luminance L₁₁; and a second color filter for viewing the secondimage, wherein the second filter transmits luminance L₂ of de-saturatedprimary color Q₁, transmits m luminances L₁, . . . , L_(m) of primary mcolors P₁, . . . , P_(m), and luminance L₂ substantially greater thanluminances P₁, . . . , P_(m).
 6. The apparatus of claim 5 wherein aprimary color P_(i) of the first image is blue and has relatively lowluminance and is transmitted by a substantial fraction by both the firstand second filters.
 7. An apparatus for displaying an anaglyphstereoscopic image, the stereoscopic image comprising a first image anda second image, said apparatus configured to: provide four spectralcomponents of light S₁, S₂, S₃, S₄ having substantially non-overlappingspectra wherein the first component is red, the third component isgreen, the second component S₂ is substantially between the firstcomponent S₁ and the third component S₃, and the third component S₃ issubstantially between the second component S₂ and the fourth componentS₄; display the first image in the first S₁ and third S₃ components; anddisplay the second image in the second S₂ and fourth S₄ components,wherein the combined second S₂ and fourth S₄ components comprise ade-saturated color.
 8. The apparatus of claim 7, further comprising:component S₂ being yellow; and component S₄ being blue.
 9. The apparatusof claim 7, further comprising: said apparatus configured to: provide afifth blue spectral component of light S₅; and display the first imagein the first S₁, third S₃, and fifth S₅ components.
 10. The apparatus ofclaim 7 further comprising: a first color filter for viewing the firstimage, wherein the first filter transmits: luminance L₁₁ of combinedfirst and third components S₁, and S₃; and luminance L₁₂ of combinedsecond and fourth components S₂, and S₄, luminance L₁₁ substantiallygreater than luminance L₁₂; and a second color filter for viewing thesecond image, wherein the second filter transmits: luminance L₂₂ ofcombined second and fourth components S₂, and S₄; and luminance L₂₁ ofcombined first and third components S₁, and S₃, luminance L₂₂substantially greater than luminance L₂₁.
 11. The apparatus of claim 7wherein fourth component S₄ has relatively low luminance and issubstantially transmitted by both the first and second filters.
 12. Anapparatus for viewing an anaglyph stereoscopic image, the image renderedin at least four spectral components comprising: a first component S₁being substantially red; a second component S₂ being substantiallybetween the first component S₁ and a third component S₃; the thirdcomponent S₃ being substantially green; and the third component S₃ beingsubstantially between the second component S₂ and a fourth component S₄,said apparatus comprising: a first color filter for viewing the imagehaving a first transmission spectrum that transmits: luminance L₁₁ ofcombined red and green components S₁ and S₃; and luminance L₁₂ ofcombined second and fourth components S₂ and S₄, luminance L₁₁substantially greater than luminance L₁₂; and a second color filter forviewing the anaglyph having a second transmission spectrum thattransmits: luminance L₂₂ of combined second and fourth components S₂ andS₄; and luminance L₂₁ of combined red and green components S₁ and S₃,luminance L₂₂ substantially greater than luminance L₂₁.
 13. Theapparatus of claim 12 wherein the first filter: transmits a substantialportion of the first component S₁; transmits a substantial portion ofthe third component S₃; and blocks a substantial portion of the secondcomponent S₂; and wherein the second filter: transmits a substantialportion of the second component S₂; transmits a substantial portion ofthe fourth component S₄; blocks a substantial portion of the firstcomponent S₁, and blocks a substantial portion of the third componentS₃.
 14. The apparatus of claim 13 wherein the first filter blocks asubstantial portion of the fourth component S₄.
 15. The apparatus ofclaim 13 wherein the first filter transmits a substantial portion of thefourth component S₄, the fourth component S₄ having low relativeluminance.
 16. The apparatus of claim 13 wherein the first filtertransmits a substantial portion of a fifth blue component S₅, the fifthcomponent S₅ having low relative luminance.
 17. The apparatus of claim13 wherein the second filter transmits a substantial portion of a fifthblue component S₅, the fifth component S₅ having low relative luminance.18. The apparatus of claim 12 wherein said first transmission spectrumand said second transmission spectrum overlap in regions of low spectralluminance.
 19. An apparatus for viewing an anaglyph stereoscopic imagecomprising: a first color filter for viewing the first image of theanaglyph, said first filter transmitting a substantial fraction of a redprimary color, said first filter transmitting a substantial fraction ofa green primary color, said first filter transmitting a substantialfraction of a blue primary color, said first filter blocking asubstantial fraction of a yellow primary color; and a second colorfilter for viewing the second image of the anaglyph, said second filtertransmitting a substantial fraction of the yellow primary color, saidsecond filter transmitting a substantial fraction of the blue primarycolor, said second filter blocking a substantial fraction of the redprimary color, said second filter blocking a substantial fraction of thegreen primary color.
 20. The apparatus of claim 19 wherein thetransmission spectrum of the first filter and the transmission spectrumof the second filter overlap in regions of low luminance.